Add ability to skip routing on a particular setRoute() call.

I'm submitting this pull request even though I'm not sure it's the proper solution.  I'd like to be able to set the route without triggering routing in a specific case.  I don't see any better way to accomplish that, but I'm open to suggestions on how this code could be improved.

As it stands, this code is fulfilling my need.  I can do:

    setRoute( someRoute, true );

and routing will not fire for that particular setRoute() call.

Please let me know what you think of this change.