Improved FileLoader to be compatible with custom jsCompilers

Hi!

For a project I'm using connect-assets-jspaths that is really great for using connect-assets with requirejs.
I was also implementing a custom jsCompilers with connect-assets (like the [jade one](https://github.com/TroyGoode/connect-assets-jade)), so I was compiling files with a custom extensions (in my case it was 'cc') differently.

My issue was that I was getting an error like "cannot find path for product.cc.js" because your FileLoader.coffee was removing the "coffee" and "js" extensions but not all of those in jsCompilers.
So I improved it to iterate through the jsCompilers of assetsModule and remove every extension in it, now it is taking into account custom js compilers. In my projects, that works perfectly now!

Tell me what you think of it.