added examples

contracts/examples/SampleTokenTimelock.sol

@@ -0,0 +1,32 @@
+pragma solidity ^0.4.24;
+
+import "../token/ERC20/ERC20Mintable.sol";
+import "../token/ERC20/ERC20Detailed.sol";
+import "../token/ERC20/TokenTimelock.sol";
+
+/**
+ * @title SampleTimelockToken
+ * @dev Very simple ERC20 Token that can be minted.
+ * It is meant to be used in a tokentimelock contract.
+ */
+contract SampleTimelockToken is ERC20Mintable, ERC20Detailed {
+    constructor() public ERC20Detailed("Sample Timelock Token", "STT", 18) {}
+}
+
+
+/**
+ * @title SampleTokenTimelock
+ * @dev This is an example of a token lock for certain time.
+ */
+
+contract SampleTokenTimelock is TokenTimelock{
+
+    constructor(
+        ERC20Mintable token,
+        address beneficiary,
+        uint256 releaseTime
+    ) 
+    public
+    TokenTimelock(token, beneficiary, releaseTime){}
+
+} 

contracts/examples/SampleTokenVesting.sol

@@ -0,0 +1,23 @@
+pragma solidity ^0.4.24;
+
+import "../drafts/TokenVesting.sol";
+
+/**
+ * @title SampleTokenVesting
+ * @dev This is an example of a token vesting for defined time period. 
+ * Tokens to be vested will be sent directly to this contract.
+ */
+
+contract SampleTokenVesting is TokenVesting{
+
+    constructor(
+        address beneficiary, 
+        uint256 start, 
+        uint256 cliffDuration, 
+        uint256 duration, 
+        bool revocable
+    ) 
+    public
+    TokenVesting(beneficiary, start, cliffDuration, duration, revocable){}
+
+}

contracts/mocks/SafeERC20Helper.sol

@@ -3,47 +3,28 @@ pragma solidity ^0.4.24;
 import "../token/ERC20/IERC20.sol";
 import "../token/ERC20/SafeERC20.sol";
 
-contract ERC20FailingMock is IERC20 {
-  uint256 private _allowance;
-  function totalSupply() public view returns (uint256) {
-    return 0;
-  }
+contract ERC20FailingMock {
+    uint256 private _allowance;
 
-  function transfer(address, uint256) public returns (bool) {
-    return false;
-  }
+    function transfer(address, uint256) public returns (bool) {
+        return false;
+    }
 
-  function transferFrom(address, address, uint256) public returns (bool) {
-    return false;
-  }
+    function transferFrom(address, address, uint256) public returns (bool) {
+        return false;
+    }
 
-  function approve(address, uint256) public returns (bool) {
-    return false;
-  }
+    function approve(address, uint256) public returns (bool) {
+        return false;
+    }
 
-  function increaseAllowance(address, uint256) public returns (bool){
-    return false;
-  }
-
-  function decreaseAllowance(address, uint256) public returns (bool){
-    return false;
-  }
-
-  function balanceOf(address) public view returns (uint256) {
-    return 0;
-  }
-
-  function allowance(address, address) public view returns (uint256) {
-    return 0;
-  }
+    function allowance(address, address) public view returns (uint256) {
+        return 0;
+    }
 }
 
-contract ERC20SucceedingMock is IERC20 {
-  uint256 private _allowance;
-
-  function totalSupply() public view returns (uint256) {
-    return 0;
-  }
+contract ERC20SucceedingMock {
+    uint256 private _allowance;
 
     function transfer(address, uint256) public returns (bool) {
         return true;
@@ -57,33 +38,20 @@ contract ERC20SucceedingMock is IERC20 {
         return true;
     }
 
-  function increaseAllowance(address, uint256) public returns (bool){
-    return true;
-  }
+    function setAllowance(uint256 allowance_) public {
+        _allowance = allowance_;
+    }
 
-  function decreaseAllowance(address, uint256) public returns (bool){
-    return true;
-  }
-
-  function balanceOf(address) public view returns (uint256) {
-    return 0;
-  }
-
-  function allowance(address, address) public view returns (uint256) {
-    return _allowance;  
-  }
-
-  function setAllowance(uint256 value) public {
-    _allowance = value;
-  }
+    function allowance(address, address) public view returns (uint256) {
+        return _allowance;
+    }
 }
 
 contract SafeERC20Helper {
+    using SafeERC20 for IERC20;
 
-  using SafeERC20 for IERC20;
-
-  IERC20 private _failing;
-  IERC20 private _succeeding;
+    IERC20 private _failing;
+    IERC20 private _succeeding;
 
     constructor () public {
         _failing = IERC20(new ERC20FailingMock());
@@ -130,23 +98,15 @@ contract SafeERC20Helper {
         _succeeding.safeIncreaseAllowance(address(0), amount);
     }
 
-  function doFailingIncreaseAllowance() public {
-    _failing.safeIncreaseAllowance(address(0), 0);
-  }
-
-  function doFailingDecreaseAllowance() public {
-    _failing.safeDecreaseAllowance(address(0), 0);
-  }
-
-  function doSucceedingTransfer() public {
-    _succeeding.safeTransfer(address(0), 0);
-  }
+    function doSucceedingDecreaseAllowance(uint256 amount) public {
+        _succeeding.safeDecreaseAllowance(address(0), amount);
+    }
 
     function setAllowance(uint256 allowance_) public {
         ERC20SucceedingMock(_succeeding).setAllowance(allowance_);
     }
 
-  function doSucceedingApprove() public {
-    _succeeding.safeApprove(address(0), 0);
-  }
-}
+    function allowance() public view returns (uint256) {
+        return _succeeding.allowance(address(0), address(0));
+    }
+}

contracts/token/ERC20/SafeERC20.sol

@@ -1,7 +1,7 @@
 pragma solidity ^0.4.24;
 
-import "./ERC20.sol";
 import "./IERC20.sol";
+import "../../math/SafeMath.sol";
 
 /**
  * @title SafeERC20
@@ -10,58 +10,31 @@ import "./IERC20.sol";
  * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
  */
 library SafeERC20 {
-  function safeTransfer(
-    IERC20 token,
-    address to,
-    uint256 value
-  )
-    internal
-  {
-    require(token.transfer(to, value));
-  }
+    using SafeMath for uint256;
 
-  function safeTransferFrom(
-    IERC20 token,
-    address from,
-    address to,
-    uint256 value
-  )
-    internal
-  {
-    require(token.transferFrom(from, to, value));
-  }
+    function safeTransfer(IERC20 token, address to, uint256 value) internal {
+        require(token.transfer(to, value));
+    }
 
-  function safeApprove(
-    IERC20 token,
-    address spender,
-    uint256 value
-  )
-    internal
-  {
-    // safeApprove should only be called when setting an initial allowance, 
-    // or when resetting it to zero. To increase and decrease it, use 
-    // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
-    require((value == 0) || (token.allowance(msg.sender, spender) == 0));
-    require(token.approve(spender, value));
-  }
+    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
+        require(token.transferFrom(from, to, value));
+    }
 
-  function safeIncreaseAllowance(
-    IERC20 token,
-    address spender,
-    uint256 addedValue
-  )
-    internal
-  {
-    require(token.increaseAllowance(spender, addedValue));
-  }
+    function safeApprove(IERC20 token, address spender, uint256 value) internal {
+        // safeApprove should only be called when setting an initial allowance,
+        // or when resetting it to zero. To increase and decrease it, use
+        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
+        require((value == 0) || (token.allowance(msg.sender, spender) == 0));
+        require(token.approve(spender, value));
+    }
 
-  function safeDecreaseAllowance(
-    IERC20 token,
-    address spender,
-    uint256 subtractedValue
-  )
-    internal
-  {
-    require(token.decreaseAllowance(spender, subtractedValue));
-  }
-}
+    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
+        uint256 newAllowance = token.allowance(address(this), spender).add(value);
+        require(token.approve(spender, newAllowance));
+    }
+
+    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
+        uint256 newAllowance = token.allowance(address(this), spender).sub(value);
+        require(token.approve(spender, newAllowance));
+    }
+}