Update SimpleToken.sol

contracts/examples/SimpleToken.sol

@@ -14,7 +14,7 @@ contract SimpleToken is StandardToken {
 
   string public constant name = "SimpleToken";
   string public constant symbol = "SIM";
-  uint256 public constant decimals = 18;
+  uint8 public constant decimals = 18;
 
   uint256 public constant INITIAL_SUPPLY = 10000;