Pydifact

- fix missing pydifact.syntax package

- Add a `split_by(tag_name)` helper to manually split segment collections

- Deprecate SegmentCollection in favour of Interchange
- Add Interchange and Message semantic and featured classes
- Add an optional predicate filter to `get_segment` and `get_segments` methods
- Allow to access AbstractSegmentsContainer elements using `container[i]`

- corrected pypi details

- First release