It seems that (at least for me) I had to type:
git clone git://github.com:jesseward/plex-lastfm-scrobbler.git
Instead of
git clone git@github.com:jesseward/plex-lastfm-scrobbler.git
For it to work. I was getting a 'Permission denied (Publickey)' error. Got it working now with the first command.
