make StandardToken state variables private

contracts/token/ERC20/BurnableToken.sol

@@ -25,21 +25,11 @@ contract BurnableToken is StandardToken {
    * @param _value uint256 The amount of token to be burned
    */
   function burnFrom(address _from, uint256 _value) public {
-    require(_value <= allowed[_from][msg.sender]);
-    // Should https://github.com/OpenZeppelin/zeppelin-solidity/issues/707 be accepted,
-    // this function needs to emit an event with the updated approval.
-    allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
-    _burn(_from, _value);
+    _burnFrom(_from, _value);
   }
 
   function _burn(address _who, uint256 _value) internal {
-    require(_value <= balances[_who]);
-    // no need to require value <= totalSupply, since that would imply the
-    // sender's balance is greater than the totalSupply, which *should* be an assertion failure
-
-    balances[_who] = balances[_who].sub(_value);
-    totalSupply_ = totalSupply_.sub(_value);
+    super._burn(_who, _value);
     emit Burn(_who, _value);
-    emit Transfer(_who, address(0), _value);
   }
-}
+}

contracts/token/ERC20/CappedToken.sol

@@ -29,7 +29,7 @@ contract CappedToken is MintableToken {
     public
     returns (bool)
   {
-    require(totalSupply_.add(_amount) <= cap);
+    require(totalSupply().add(_amount) <= cap);
 
     return super.mint(_to, _amount);
   }

contracts/token/ERC20/MintableToken.sol

@@ -41,10 +41,8 @@ contract MintableToken is StandardToken, Ownable {
     canMint
     returns (bool)
   {
-    totalSupply_ = totalSupply_.add(_amount);
-    balances[_to] = balances[_to].add(_amount);
     emit Mint(_to, _amount);
-    emit Transfer(address(0), _to, _amount);
+    _mint(_to, _amount);
     return true;
   }
 

contracts/token/ERC20/StandardToken.sol

@@ -14,11 +14,11 @@ import "../../math/SafeMath.sol";
 contract StandardToken is ERC20 {
   using SafeMath for uint256;
 
-  mapping(address => uint256) balances;
+  mapping (address => uint256) private balances;
 
-  mapping (address => mapping (address => uint256)) internal allowed;
+  mapping (address => mapping (address => uint256)) private allowed;
 
-  uint256 totalSupply_;
+  uint256 private totalSupply_;
 
   /**
   * @dev Total number of tokens in existence
@@ -156,4 +156,22 @@ contract StandardToken is ERC20 {
     return true;
   }
 
+  function _mint(address _account, uint256 _amount) internal {
+    totalSupply_ = totalSupply_.add(_amount);
+    balances[_account] = balances[_account].add(_amount);
+    emit Transfer(address(0), _account, _amount);
+  }
+
+  function _burn(address _account, uint256 _amount) internal {
+    totalSupply_ = totalSupply_.sub(_amount);
+    balances[_account] = balances[_account].sub(_amount);
+    emit Transfer(_account, address(0), _amount);
+  }
+
+  function _burnFrom(address _account, uint256 _amount) internal {
+    // Should https://github.com/OpenZeppelin/zeppelin-solidity/issues/707 be accepted,
+    // this function needs to emit an event with the updated approval.
+    allowed[_account][msg.sender] = allowed[_account][msg.sender].sub(_amount);
+    _burn(_account, _amount);
+  }
 }