update grunt file to put everything in dist/dev and dist/prod. 

This pull gives us a dist folder similar to what was detailed in issue #21. The only difference is that I created a dev folder where css and js was not minified/compressed and a prod folder where they are. If everyone's OK with the changes I'll merge them.

Thanks,
Jon
It's been on my todo to keep the license info a la https://github.com/mootools/mootools-core/pull/2635/files

If you wanted to add that...