Last.fm Now Playing module

This pull request adds the module `bones.modules.lastfm.Lastfm`, which adds a "now playing" feature for last.fm users.

Triggers:
`+lastfm [-rd] [nickname]`
~~~~
Flags (Optional):
   -r nickname:
   Register the provided Last.fm username to your nickname

   -d:
   Remove a registered last.fm account from your nickname

Arguments:
   nickname (Optional):
   If provided, +lastfm will check the status of the account connected to the specified nickname.
~~~~

The database may be initialized by running the following command from the Bones root directory:
`python -m bones.modules.lastfm config.ini`
You need to replace config.ini with the name of your configuration file.