Travis CI: site documentation update at 2014-02-08 09:02:30 UTC.

Commit: https://github.com/urho3d/Urho3D/commit/a770760eb5deea30158ea14023e4628beb2a5331

Message: For Travis CI - Install rake into global gem set.

It was not neccessary before but somehow all the Travis CI build environment for C++ language today do not have rake pre-installed anymore.