The RB.TextBasedReviewableView was using an incorrect root path

Instead of just being the path relative to the FQDN, it was using the

entire URL. This resulted in Backbone never matching URLs since it was

trying to match fragments against full URLs. The view would then be

stuck in the rendered view mode at all times.

Verified that the TextBasedReviewableView can switch between rendered

and source modes on Python 2.7, 3.5, 3.6, and 3.7.