fix identation and some linter warnings

contracts/crowdsale/distribution/PostDeliveryCrowdsale.sol

@@ -41,6 +41,5 @@ contract PostDeliveryCrowdsale is Initializable, TimedCrowdsale {
         _balances[beneficiary] = _balances[beneficiary].add(tokenAmount);
     }
 
-
     uint256[50] private ______gap;
 }

contracts/mocks/ForceEther.sol

@@ -8,7 +8,9 @@ pragma solidity ^0.5.0;
 // @author Remco Bloemen <remco@neufund.org>
 contract ForceEther {
 
-    constructor() public payable { }
+    constructor() public payable {
+        // solhint-disable-previous-line no-empty-blocks
+    }
 
     function destroyAndSend(address payable recipient) public {
         selfdestruct(recipient);

contracts/mocks/MessageHelper.sol

@@ -40,7 +40,7 @@ contract MessageHelper {
     }
 
     function call(address _to, bytes memory _data) public returns (bool) {
-        // solium-disable-next-line security/no-low-level-calls
+        // solhint-disable-next-line security/avoid-low-level-calls
         (bool success,) = _to.call(_data);
         if (success)
             return true;

contracts/token/ERC20/TokenTimelock.sol

@@ -21,6 +21,7 @@ contract TokenTimelock is Initializable {
     uint256 private _releaseTime;
 
     function initialize (IERC20 token, address beneficiary, uint256 releaseTime) public initializer {
+        // solhint-disable-next-line not-rely-on-time
         require(releaseTime > block.timestamp);
         _token = token;
         _beneficiary = beneficiary;

contracts/token/ERC721/ERC721Metadata.sol

@@ -38,7 +38,8 @@ contract ERC721Metadata is Initializable, ERC165, ERC721, IERC721Metadata {
 
     function _hasBeenInitialized() internal view returns (bool) {
         return supportsInterface(_INTERFACE_ID_ERC721_METADATA);
-}
+    }
+
     /**
      * @dev Gets the token name
      * @return string representing the token name