Gender of signer is irrelevant and distracting (#822)

contracts/ECRecovery.sol

@@ -10,7 +10,7 @@ pragma solidity ^0.4.18;
 library ECRecovery {
 
   /**
-   * @dev Recover signer address from a message by using his signature
+   * @dev Recover signer address from a message by using their signature
    * @param hash bytes32 message, the hash is the signed message. What is recovered is the signer address.
    * @param sig bytes signature, the signature is generated using web3.eth.sign()
    */