Create users instead of new-ing them

This causes them to be persisted in Redis.
Only pass room id to Source

The adapter interface is only expecting a unique identifier, not the whole room.
Add myself to authors in the gemspec
Use fetch_room instead of Campfire#find_room_by_id
Create user for all the users in a room upon join
Merge pull request #4 from zacstewart/master

Create users upon joining a room