Do not use implicit type conversion for address literals (#1002)

Uses the explicit address(0) for the zero address

contracts/examples/SimpleSavingsWallet.sol

@@ -32,7 +32,7 @@ contract SimpleSavingsWallet is Heritable {
    * @dev wallet can send funds
    */
   function sendTo(address payee, uint256 amount) public onlyOwner {
-    require(payee != 0 && payee != address(this));
+    require(payee != address(0) && payee != address(this));
     require(amount > 0);
     payee.transfer(amount);
     emit Sent(payee, amount, address(this).balance);