Move guiders submodule into this repository (GuidedTour)

Move in the required files from the Guiders repo to an equivalent
directory.

This will give us more scope for refactoring.  We will be able to have
deeper integration to MediaWiki where appropriate, and no longer need to
maintain backwards compatibility with users of upstream Guiders.

This commit only does the structural changes, and minimal comments.
The next one will get jshint passing and do small additional style
changes.

Also update README, mostly related to this change.

Change-Id: I02df756f08b4d22749d3bcee1de8df6084609285