Transitions

- Bugfix 314: Do not override already defined model functions with convenience functions (thanks Arkanayan)
- Bugfix 316: `state.Error` did not call parent's `enter` method (thanks potens1)

- Bugfix 301: Reading `Readme.md` in `setup.py` causes a `UnicodeDecodeError` in non-UTF8-locale environments (thanks jodal)

Release 0.6.7 is identical to 0.6.6. A release had been necessary due to 294 related to PyPI.

- Bugfix: `HierarchicalMachine` now considers the initial state of `NestedState` instances/names passed to `initial`.
- Bugfix: `HierarchicalMachine` used to ignore children when `NestedStates` were added to the machine.
- Bugfix 300: Fixed missing brackets in `TimeoutState` (thanks Synss)
- Feature 289: Introduced `Machine.resolve_callable(func, event_data)` to enable customization of callback definitions (thanks ollamh and paulbovbel)
- Feature 299: Added support for internal transitions with `dest=None` (thanks maueki)
- Feature: Added `Machine.dispatch` to trigger events on all models assigned to `Machine`

- Feature 287: Embedding `HierarchicalMachine` will now reuse the machine's `initial` state. Passing `initial: False` overrides this (thanks mrjogo).
- Bugfix 292: Models using `GraphMashine` were not picklable in the past due to `graph` property. Graphs for each model are now stored in `GraphMachine.model_graphs` (thanks ansumanm).

- Bugfix 274: `initial` has not been passed to super in `HierachicalMachine.add_model` (thanks to illes).
- Feature 275: `HierarchicalMachine.add_states` now supports keyword `parent` to be a `NestedState` or a string.
- Bugfix 278: `NestedState` has not been exited correctly during reflexive triggering (thanks to hrsmanian).