Pass an array of cookies to the webLogOn callback
This eliminates the extra step of splitting the string when adding them to a request jar
Add loggedOn property, remove 'disconnected' event
- Emit 'loggedOff' whenever loggedOn changes to false
- Remove _preventReconnect, instead simply forget about the socket
Reset users and chatRooms on logon
- The growth of the users object is now at least bounded by Steam's uptime
- Accessing these properties while not logged on is no longer supported
Add logOff

Additionally, allow calling logOn at any time
Closes #23
Improve friend and group handling
- Adds friends and groups properties and a 'relationships' event
- Replaces 'relationship' event with 'friend' and 'group'
- Closes #24
Rename 'personaState' into 'user' for consistency