Require kernel change

I forked the require kernel so I could make some changes

Mostly the performance (due to # of http requests) was too poor.

https://github.com/ether/etherpad-require-kernel/blob/master/kernel.js#L456 shows the change I made.

We still need to address the issue of it not loading modules that don't serve their main file as ``/index.js``

It needs a lot of testing, I didn't test IE.

So why this version:

 -[ ] Reduce # of http requests
 -[ ] Allow loading of modules that don't load from index.js