Tmuxp

- The `--force` was not with us.

- 72 Create destination directory if it doesn't exist. Thanks
[ThiefMaster].
- New context manager for tests, `temp_session`.
- New testsuite, `testsuite.test_utils` for testing testsuite
tools.
- New command, `before_script`, which is a file to
be executed with a return code. It can be a bash, perl, python etc.
script.
- 56 {ref}`python_api_quickstart <libtmux:quickstart>`

- 55 where tmuxp would crash with letter numbers in version.
Write tests.

- {meth}`Window.split_window()` now allows `-c start_directory`.
- 35 Builder will now use `-c start_directory` to
create new windows and panes.

This removes a hack where `default-path` would be set for new pane and
window creations. This would bleed into tmux user sessions after
creations.

- section heading normalization.
- tao of tmux section now treated as a chatper. tao of tmux may be
split off into its own project.
- use conventions from [tony/cookiecutter-pypackage].

- Fix `$ tmuxp freeze` CLI output.
- Update `_compat` support module.
- Fix extra space in [PEP 263].