Fixes DEVELOPER-686

Using a new transformer to look at links and add the "external-link" css
class if it is linking to something off the `site.base_url` domain.

Fixing false positive results for external links

Better fix for searching for non text children
Adding (or removing) external link icons

Buzz and projects, also fixing up the display on the right bars.

More fixes for DEVELOPER-686

* Removed some explicit external link icons
* Fixing up the product get started buzz icons
* Removing extra space from product get involved link
Merge pull request #352 from LightGuard/DEVELOPER-686

Fixes DEVELOPER-686