Special indent for HTML/CSS/SASS/JS/COFFEE files

These files get a special 2-space indent. Specially HTML, it
gets deep as fuck, making the text often bypass the 80 character
limit. I don't feel comfortable on doing that.

Other related files such as CSS/SASS and JS/CoffeeScript files
will follow this rule too; and depending on how happy am I, I'll
extend this rule to other file types such as Python or Ruby.

Needless to say that these modifications are living on vimrc for
now. If this thing gets messy at some point I'll just move these
modifications to ftplugin folder.
Add support for CoffeeScript