Transitions

- Documentation: Add docstring to every public method
- Bugfix 257: Readme example variable had been capitalized (thanks to fedesismo)
- Add `appveyor.yml` for Windows testing; However, Windows testing is disabled due to 258
- Bugfix 262: Timeout threads prevented program from execution when main thread ended (thanks to tkuester)
- `prep_ordered_arg` is now protected in `core`
- Convert `logger` instances to `_LOGGER` to comply with protected module constant naming standards
- `traverse` is now protected in `HierarchicalMachine`
- Remove abstract class `Diagram` since it did not add functionality to `diagrams`
- Specify several overrides of `add_state` or `add_transition` to keep the base class parameters instead of `*args` and `**kwargs`
- Change several `if len(x) > 0:` checks to `if x:` as suggested by the static code analysis to make use of falsy empty lists/strings.

- Feature 245: Callback definitions ('before', 'on_enter', ...) have been moved to classes `Transition` and `State`
- Bugfix 253: `Machine.remove_transitions` converted `defaultdict` into dict (thanks Synss)
- Bugfix 248: `HierarchicalStateMachine`'s copy procedure used to cause issues with function callbacks and object references (thanks Grey-Bit)
- Renamed `Machine.id` to `Machine.name` to be consistent with the constructor parameter `name`
- Add `Machine.add_transitions` for adding multiple transitions at once (thanks Synss)

- `add_state_features` convenience decorator supports creation of custom states
- `Tags` makes states taggable
- `Error` checks for error states (not accepted states that cannot be left); subclass of `Tags`
- `Volatile` enables scoped/temporary state objects to handle context parameters
- Removed `add_self` from `Machine` constructor
- `pygraphviz` is now optional; use `pip install transitions[diagrams]` to install it
- Narrowed warnings filter to prevent output cluttering by other 3rd party modules (thanks to ksandeep)
- Reword HSM exception when wrong state object had been passedn (thanks to Blindfreddy)
- Improved handling of partials during graph generation (thanks to Synss)
- Introduced check to allow explicit passing of callback functions which match the `on_enter_<state>` scheme (thanks to termim)
- Bug 243: on_enter/exit callbacks defined in dictionaries had not been assigned correctly in HSMs (thanks to Blindfreddy)
- Introduced workaround for Python 3 versions older than 3.4 to support dill version 0.2.7 and higher (thanks to mmckerns)
- Improved manifest (242) to comply with distribution standards (thanks to jodal)

- Bug 214: `LockedMachine` as a model prevented correct addition of `on_enter/exit_<state>` (thanks to kr2)
- Bug 217: Filtering rules for auto transitions in graphs falsely filtered certain transitions (thanks to KarolOlko)
- Bug 218: Uninitialized `EventData.transition` caused `AttributeError` in `EventData.__repr__` (thanks to kunalbhagawati)
- Bug 215: State instances passed to `initial` parameter of `Machine` constructor had not been processed properly (thanks mathiasimmer)

- Bug 213: prevent `LICENSE` to be installed to root of installation path

- Added reflexive transitions (thanks to janLo)
- Wildcards for reflexive (`wildcard_same`) and all (`wildcard_all`) destinations are `Machine` class variables now which can be altered if necessary.
- Add LICENSE to packaged distribution (thanks to bachp)
- Bug 211: `prepare` and `finalized` had not been called for HierarchicalMachines (thanks to booware)