1.1.0

• Prometheus.GHC.ghcStats now has the type m (Maybe (IO ThreadId)).

  This was changed to clarify what happens if GC stats aren't enabled, in which case you'll just get Nothing back.

  Don't forget to actually run the stats collector thread though! For example,

  (startGhcStats, registry) <- buildRegistry ghcStats
  for_ startGhcStats id
  

1.0.0

Initial release.