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
Needs to be changed to "0 values in length properties". Specifying `0` for things like duration instead of `0s` blows up in FF.