Moves require to inside decryption context

There was an issue where if a require was actually a function call itself (leveraging middleware), it would run outside the context  of decryption and could cause issues.

src/decryptors/nodejs4.3/_serverless_handler.js

@@ -7,10 +7,9 @@ for (var key in envVars) {
   process.env[key] = envVars[key];
 }
 
-var originalHandler = __HANDLER_REQUIRE__;
-
 module.exports.handler = function(event, context, callback) {
   decryptor(function(){
+    var originalHandler = __HANDLER_REQUIRE__;
     return originalHandler(event, context, callback);
   });
 };