Add CoffeeScript support

[nickdima]

Add the abbility to require coffescript files that contain JSX wrapped in backticks by specifying the .coffee extension like so:

require('node-jsx').install({extension: '.coffee'})

Then simply require your coffeescript module just like a js one, without specifying its extension.

[petehunt]

How about an "additionalTransform" option that is a function the user provides? That way we can break the dependency on coffeescript for users who don't use it and can support other compile to js languages. Seem reasonable?

[nickdima]

That's a great idea! I'll do that. Thanks Pete!

[nickdima]

Added additionalTransform option to install function for performing an additional transform on the source file before the react transform. Here's an example with coffeescript transform:

coffee = require('coffee-script');
require('node-jsx').install({
  extension: '.coffee',
  additionalTransform: function(src) {
    return coffee.compile(src, {
      'bare': true
    });
  }
});

[petehunt]

Thanks for this!