Adding avatar functionality to timberComment (again) this time with some tests

Not sure if these tests are that great.  I'm also not 100% sure i like the magic relative url => absolute url aspect.  

Still, its working ok, and the tests pass.  in fact just the tests running at all was a major victory : ) 

As before, don't feel you have to use this  or be gentle with the feedback.  I'm well out of my wordpress depth here.