Mutwo.timeline

Added
- `is_conflict` keyword argument to `timeline_interfaces.TimeLine.resolve_conflicts`, see [here](https://github.com/mutwo-org/mutwo.timeline/commit/0e8fd2e7dba170c60803c1b01d6b6ccab02471f3)

Changed
- Order of 'TaggedSimultaneousEvent' in 'SimultaneousEvent' returned by 'TimeLineToSimultaneousEvent' is always the same now, see [here](https://github.com/mutwo-org/mutwo.timeline/commit/8931903a76aac5d0e46bca061478f69ed65c3442)

Fixed
- `TimeLine.resolve_conflicts`: Fix for inbetween event, see [here](https://github.com/mutwo-org/mutwo.timeline/commit/9d067cb475554b74ffdfe83c4017eeebd40a999d)
- `TagCountStrategy`: it returns results in correct order now, see [here](https://github.com/mutwo-org/mutwo.timeline/commit/19481e89a4cdd284ff1e8d59cf59543f369c2908)
- `TimeLineToSimultaneousEvent`: Fix conversion of empty `EventPlacement`, see [here](https://github.com/mutwo-org/mutwo.timeline/commit/026b83c9be16cf54d2cc64623ceb19890da11686)

Added
- `timeline_interfaces.TimeLine.resolve_conflicts` [to fix overlapping conflicts](https://github.com/mutwo-org/mutwo.timeline/commit/4e0153851cd7a51daa9b3530acfed53b18c422be)
- `timeline_interfaces.TimeLine.unregister` [to unregister `EventPlacement` from a time line](https://github.com/mutwo-org/mutwo.timeline/commit/17f42450a45baca0115f5f3b2b06ad5e765d31c4)

Added
- `timeline_converters.EventPlacementTupleToGaplessEventPlacementTuple`
- `timeline_converters.EventPlacementTupleToSplitEventPlacementDict`
- `timeline_converters.TimeLineToEventPlacementTuple`

Changed
- `timeline_events` to `timeline_interfaces` [see here](ab2cb2bbc086014eb9b60db26679409a36142d68)
- `timeline_events.TimeLine` to `timeline_interfaces.TimeLine`
- `timeline_events.EventPlacement` to `timeline_interfaces.EventPlacement`
- `EventPlacement` to support multiple tagged events in the same `EventPlacement`

Removed
- overlap checks in `TimeLine.register`
- `timeline_converters.EventPlacementTupleToSequentialEvent`: replaced by more powerful `timeline_converters.TimeLineToSimultaneousEvent`

Initial release of `mutwo.timeline`.