Bistiming

New
- update CI and support Python 3.9 (27)
- log "got exception in ..." if an error occurs during the context manager (29)
- add `MultiStopwatch.format_statistics()` (30)

New
- add new class `MultiStopwatch` (18)

New
- finished the documentation

Change
- replace "splitted" with "split" because "splitted" is not a standard English word (16)

Change
- remove `IterTimer` (2)
- change `SimpleTimer` to `Stopwatch`, though `SimpleTimer` can still be used for backward-compatibility (9)
- change some variables `Stopwatch` (`start_time`, `end_time` and `elapsed_time`) to have `_` prefix (10)

New
- add public `start()`, `pause()`, `split()`, `reset()`, `get_elapsed_time()`, `get_cumulative_elapsed_time()` and `log_elapsed_time()` methods to `Stopwatch` (3, 4, 12)
- add `verbose` parameter to `Stopwatch.__init__()` (8)

Change
- `SimpleTimer`'s `end_in_new_line=False` not rewrite the line (fixed 1)

Fix
- fix Python 2 `print` function bug
- fix `__version__` getting bug

New
- implement `SimpleTimer` and `IterTimer`
- add the examples for `SimpleTimer` and `IterTimer`
- add `setup.py` and testing configuration