pytransitions/transitions: Release 0.8.10

Release 0.8.10 is a minor release and contains two bug fixes for the HSM extension and changes how the 'self' literal string is handled. Feature #545: The literal 'self' (default model parameter of Machine) has been replaced by the class variable Machine.self_literal = 'self'. Machine now performs an identity check (instead of a value check) with mod is self.self_literal to determine whether it should act as a model. While 'self' should still work when passed to the model parameter, we encourage using Machine.self_literal from now on. This was done to enable easier override of Machine.__eq__ in subclasses (thanks @VKSolovev). Bug #547: Introduce HierarchicalMachine.prefix_path to resolve global state names since the HSM stack is not reliable when queued=True (thanks @jankrejci). Bug #548: HSM source states were exited even though they are parents of the destination state (thanks @wes-public-apps)