Lastfm

added support for Last.fm
==================

now Rockstar gem (for last.fm API) is required.

added commands
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!lastsong : shows the last song you're scrobbled through last.fm
!lastfmuser add <lastfmnick> : add a relation between the user who's issuing the command and the <lastfmnick>. when the user issues !lastsong, Descartes will check these relations and retrieves data from the given username
!lastfmuser remove <ircnick> : removes the relation built for a given ircnick. 

you have to add two files under "reply" folder
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* lastfm.yml
* lastfm_nicks.yml

the first contains the api_key and the api_secret you have to submit to Last.fm.
the second contains a list of nicks: you can leave it empty and add with !lastfmuser add <lastfmnick>