Log-rate-limit

Changed

- Default rate-limiting now applies to identical log messages (instead of to logs originating from the same line of code).
- Replaced boolean `all_unique` parameter with `default_stream_id` which can have multiple options, including ones that achieve the same functionality as before:
- `default_stream_id=None` (or `default_stream_id=DefaultSID.NONE`) is equivalent to `all_unique=False`.
- `default_stream_id="file_line_no"` (or `default_stream_id=DefaultSID.FILE_LINE_NO`) is equivalent to `all_unique=True`.

Added

- New `default_stream_id` parameter includes a third option that wasn't previously available:
- `default_stream_id="log_message"` (or `default_stream_id=DefaultSID.LOG_MESSAGE`) which will set the default stream ID such that repeated log messages will be rate limited.

Added

- Add methods `trigger()`, `should_trigger()` and `reset_trigger()` that are used to evaluate rate-limiting and trigger logs. These functions can also be used separately from logging for other purposes, e.g. to trigger custom rate-limited events.

Changed

- Expanded usage examples in documentation, as well as other small improvements.
- Slight spacing change to default summary message.

Added

- Allow summary message to contain `stream_id` and `period_sec`.

Fixed

- Set PyPI package description.

Initial release to PyPI.