Implemented summoner model.

Used virtus.  Worked well.  One thing I don't like about Virtus that I never noticed before is the lack of easy coercion.  For example, one of the fields the API returns is the date in milliseconds.  In Ruby you have to do

`Time.at millis / 1000.0`

but I can't see an easy way to do that in Virtus.  Not sure if that'll bite us in the ass later.

I'm rushing to finish before dinner so no tests yet.  I'll get to those tomorrow.

I did get cute w/ some meta programming on how to create the model object in each resource.  I'll make a separate PR for that since it might be a bit **too** cute. :)