Merge pull request #22 from SpringRole/kar2905-patch-1

update comments

Author: kar2905

contracts/SRTToken.sol

@@ -73,6 +73,8 @@ contract StandardToken is ERC20 {
 
     /**
     * @dev Aprove the passed address to spend the specified amount of tokens on behalf of msg.sender.
+    * This only works when the allowance is 0. Cannot be used to change allowance. 
+    * https://github.com/ethereum/EIPs/issues/738#issuecomment-336277632
     * @param _spender The address which will spend the funds.
     * @param _value The amount of tokens to be spent.
     */