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
We might want to create a whitespace style guide that covers the general rules and then have each style guide reference that and add to it. This would include indentation with tabs, no trailing whitespace, line length limits, spacing for commas, semicolons, parens, braces, etc.