Add support for nested TimeMachineT

[uhbif19]

My usecase: I want to stop time and then advance time on top of it

It seems like changing instance (MonadIO m) => MonadTime (TimeMachineT m) into instance (MonadTime m) => MonadTime (TimeMachineT m)would do that. Also using instead of time passedrealCurr <- liftIO T.getCurrentTimea pair of original time and time passed which will be implemented by anyMonadTime` instance. Could write PR on that.