Mytextgrid

- Interval and Point tiers requires a parent tier

**Full Changelog**: https://github.com/rolandomunoz/mytextgrid/compare/v0.7.0...v0.8.0

- add: read textgrids from stream
- doc: more documentation

- fixed: write to TextGrid
- fixed: read TextGrid when a tier name is empty
- User hatch for packaging

- doc: Update documentation to match new changes
- add: write() method add <absent> if the TextGrid is empty.

**Full Changelog**: https://github.com/rolandomunoz/mytextgrid/compare/v0.5.0...v0.6.0

- refactor: simplify code.
- deprecated: methods to manipulate tiers from TextGrid objects.
- doc: more docstrings.
- deprecated: Remove write TextGrid as CSV.
- Rename files.

- Add more documentation