Travis CI: site documentation update at 2014-11-26 09:19:14 UTC.

Commit: https://github.com/urho3d/Urho3D/commit/e0d13d706ef8789debaa95317da27636ad6cd35f

Message: For Travis CI - simplify the ci_rebase rake task.
On normal commit, use the origin/master. On git tagging commit, use the 'tag' branch.
Also when on git taggig commit, prevent API doc update on the master branch because it is already too late to do so as the commit won't be in the tag anyway.