82 -  CSS style guide

A proposed style guide to cover CSS code commits to the jQuery projects.  Open to suggestion for rules, this pass is based on the CSS in jQuery Mobile and jQuery UI.

Based off of Issue https://github.com/jquery/contribute.jquery.org/issues/82
Two more notes that should be made here.

1.) Do not use more then 31 imports in a single css file it will break IE.
2.) Do not nest imports. When you nest imports you no longer guarantee their order.