Updates:

- watch coffeescript files too (+4 squashed commits)
- watch .{css,sass,scss,less,styl} extensions
update less support
- move comment block explaining gruntfile
  setup to NOTES_ABOUT_COMMENTS,
  there seems to be an error parsing the file
  when its in place
- use screen.css in dist/index.html
- explain requirejs build dev vs production
- update tests for generating special case files
  (e.g., sass/less/stylus) used by grunt
- add test for dist/index.html