Added examples of tokenvesting and tokentimelock

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

@@ -109,4 +109,4 @@ contract SafeERC20Helper {
     function allowance() public view returns (uint256) {
         return _succeeding.allowance(address(0), address(0));
     }
-}
+}

contracts/token/ERC20/IERC20.sol

@@ -20,4 +20,4 @@ interface IERC20 {
     event Transfer(address indexed from, address indexed to, uint256 value);
 
     event Approval(address indexed owner, address indexed spender, uint256 value);
-}
+}

contracts/token/ERC20/SafeERC20.sol

@@ -37,4 +37,4 @@ library SafeERC20 {
         uint256 newAllowance = token.allowance(address(this), spender).sub(value);
         require(token.approve(spender, newAllowance));
     }
-}
+}