Rename files with partial content. Uses the p...

...artial notation of middleman/rails etc.

This is related to PR https://github.com/CocoaPods/beta.cocoapods.org/pull/28.

It contains 2 main changes:
- Renaming shared partials to be able to use middleman's partial method (see https://github.com/CocoaPods/beta.cocoapods.org/pull/28).
- Highlight the about tab correctly (Fixing https://github.com/CocoaPods/beta.cocoapods.org/issues/27).

Up as a PR for discussion.