Proxy plugin is working! 

:boom: The clickable detector is working!

Thanks to the JavaScript interceptor by @amesbah and the Proxy plugin by [LittleProxy](https://github.com/adamfisk/LittleProxy) we can now intercept JavaScript and detect clickables.

@amesbah Give it a try before merging. The [ClickableDetectorTest](https://github.com/crawljax/crawljax/blob/17c2a1d9ae4a97365bc7b4a37fa6004bcde9505d/plugins/clickable-detector/src/test/java/com/crawljax/plugins/clickable_detector/ClickableDetectorTest.java) will show the magic.

The plugin is build in such a way that we can intercept other JavaScript as well.  

*note: it is not compatible with PhantomJS which crashes on the mutation script*.