Change extension from `.js.module` to `.module.js`

[josh]

Bonus

• Use sprockets global registry
• Adding //= require commonjs to each file is no longer needed

This also requires some new features in sprockets/master. Which I think I'm probably going to release as 2.4 since it adds new apis.

If you could give all this and sprockets/master a spin, I can cut a new release asap.

https://github.com/sstephenson/sprockets/compare/v2.3.2...master

[maccman]

This is pretty awesome - thanks!

[maccman]

I've just given it a whirl, and it works really well.

[josh]

K, Sprockets 2.4 is out