Refactor Lastfm module to return a constructor

* Update lastfm module to use internal methods
* Create a private session variable
* Update tests to use Lastfm.create
* Should enable multple Lastfm modules with different sessions to be
created. ie. to scrobble to different accounts
Create ScrobbleShift module

* Move scrobble shift logic into a module with a constructor
* Pass in a scheduler and lastfm instance
* Create tests for scrobble shift behaviour
* Update app to use new scrobble shift module
* Delete non environment config