Added methods

Hey, I added a bunch of methods to client.rb.  Thanks for the library!

Backstory:
Grooveshark is steadily removing songs (from general use, as well as my library and favorites list, but they stick around in the profile log for some reason), so I wanted to get a record of all the songs I've played.  Finding your API, I wrote "getAllUserFeed", which retrieves the entire profile log.  While I was at it, I figured I'd add some other functions, too.  I've added all the ones I saw with Firebug (except for markSongComplete, kinda - it's there, but requires inscrutably formatted input).  Anyway, thanks!