在js和native里都添加两个共同处理

[devliuhuan]

1、如果没有注册过调用的方法名，则回调提示“NoMethodInXX”
2、添加JS和原生获取对方已经注册过的方法

Before your create your PR:

Please add tests for any new or changed functionality!

1. Edit Tests/WebViewJavascriptBridgeTests/BridgeTests.m
2. Create a new test which demostrates your changes.
3. Run make test and make sure your test is passing
4. That's it!

Thanks for improving WebViewJavascriptBridge!

Cheers,
@marcuswestin