Methods to customize room member values

Users/Connections were stored in redis chatRooms, but custom data was not. This PR defines some default methods that can be over written as needed to store whatever the user wants to store.

In my case, it was userId values. I wanted to know who was in a room, but just getting back a connection.id was annoying. Instead of lots of connection checks with RPC or something, this just stores the data in redis (user beware redis implications, if any).

This is all in relation to [a thread on the message board](https://groups.google.com/forum/?fromgroups=#!topic/actionhero-js/aNqy5_TP5Jg).