Shortcodes: Module Info updates

The module info included references to `[audio]` and `[upcomingevents]` that shouldn't be there and didn't include the `[gist]` shortcode.

There are a few others that Jetpack has, but there isn't WP.com documentation to point to, so punting those until later.
Should not drink scotch, watch a movie, and read pull requests at the same time :S. Our existing code disables the Jetpack audio shortcode for WordPress versions greater than 3.6