Added Summoner#names api call.

I need to post on Riot's boards that this method seems pointless.  All it returns are the summoner names.  If you want more info you'll have to make a second call using "by name".  And let's say you want more info for *all* the summoners you're searching now you're talking about N+1 API calls.  Stupid.

Anyway, this is done.  Tests are green.