Inform

- Added *formatter* argument to *plural*.
- Added *formatter* argument to *truth*.
- Added *all* *stream_policy*.
- Added *tree()* function.

- Added *remove* argument to *full_stop*.
- Support negative widths in *ProgressBar*.

Improve documentation

- Added *truth* utility class.
- Added *render_num* argument to *plural* class.
- Added *errors* *stream_policy*.
- Improved handling of *BrokenPipeErrors*.

- Change *strip_nl* keys for *dedent()*.
- Added *include_codicil* argument to *Error.render()*.

- Use critical urgency by default with notifier if message is an error.
- Ignore *BrokenPipeError*.
- Add *full_width* argument to *render_bar*().
- Require secondary arguments to *Color* be keyword arguments.
- Require secondary arguments to *plural* be keyword arguments.
- Add *max_col_width* parameter to *columns*().
- Added type hints.