Fix issue with links in description/testing done.

When clicking a link inside the element, stop propagation of the click event so
that the link works like normal.

Also tighten up the code is no longer necessary in the mouseup event because
the click handles the same thing.

Testing Done:
Tested on my mac in Chrome, Firefox, and Safari (sorry I don't have any IE
handy to test with):
* Clicking a link opens in a new tab. It no longer opens the editor either if
  you have permission to edit.
* Clicking and dragging, mouseup on the link selects the text, doesn't open the
  editor
* Clicking anywhere else still opens the editor.

Bugs closed: 3377

Reviewed at https://reviews.reviewboard.org/r/5985/
Add release notes for Djblets 0.8.4.

This covers all the changes made since the 0.8.3 release.

Reviewed at https://reviews.reviewboard.org/r/5949/
Release Djblets 0.8.4.
Bump to 0.8.5 dev.
Merge branch 'release-0.8.x'