Travis CI: site documentation update at 2014-01-24 07:33:28 UTC.

Commit: https://github.com/urho3d/Urho3D/commit/39e13d49c8f884c8594a5b6783041d3591a65338

Message: Renamed the plane intercept parameter to "d" and reversed its sign so that it fits the conventional plane formula ax + by + cz + d = 0.