Mss

base.py
- Added the `ScreenShot` class containing data for a given screen shot (support the Numpy array interface [`ScreenShot.__array_interface__`])
- Added `shot()` method to `MSSBase`. It takes the same arguments as the `save()` method.
- Renamed `get_pixels` to `grab`. It now returns a `ScreenShot` object.
- Moved `to_png` method to `tools.py`. It is now a simple function.
- Removed `enum_display_monitors()` method. Use `monitors` property instead.
- Removed `monitors` attribute. Use `monitors` property instead.
- Removed `width` attribute. Use `ScreenShot.size[0]` attribute or `ScreenShot.width` property instead.
- Removed `height` attribute. Use `ScreenShot.size[1]` attribute or `ScreenShot.height` property instead.
- Removed `image`. Use the `ScreenShot.raw` attribute or `ScreenShot.rgb` property instead.
- Removed `bgra_to_rgb()` method. Use `ScreenShot.rgb` property instead.

darwin.py
- Removed `_crop_width()` method. Screen shots are now using the width set by the OS (rounded to 16).

exception.py
- Renamed `ScreenshotError` class to `ScreenShotError`

tools.py
- Changed signature of `to_png(data, monitor, output)` to `to_png(data, size, output)` where `size` is a `tuple(width, height)`

- MSS: better use of exception mechanism
- Linux: use of hasattr to prevent Exception on early exit
- Mac: take into account extra black pixels added when screen with is not divisible by 16 (fixes 14)
- doc: add an example to capture only a part of the screen
- :heart: contributors: David Becker, redodo

- change license to MIT
- MSS: add type hints
- MSS: remove unused code (reported by `Vulture`)
- Linux: remove MSS library
- Linux: insanely fast using only ctypes
- Linux: skip unused monitors
- Linux: use `errcheck` instead of deprecated `restype` with callable (fixes 11)
- Linux: fixed security issue (reported by Bandit)
- doc: add documentation (fixes 10)
- tests: add tests and use Travis CI (fixes 9)
- :heart: contributors: cycomanic

- add issue and pull request templates
- split the module into several files
- MSS: a lot of code refactor and optimizations
- MSS: rename `save_img()` to `to_png()`
- MSS: `save()`: replace `screen` argument by `mon`
- Mac: get rid of the `PyObjC` module, 100% ctypes
- Linux: prevent segfault when `DISPLAY` is set but no X server started
- Linux: prevent segfault when Xrandr is not loaded
- Linux: `get_pixels()` insanely fast, use of MSS library (C code)
- Windows: screen shot not correct on Windows 8 (fixes 6)

- MSS: fixed non existent alias

- MSS: `libpng` warning (ignoring bad filter type) (fixes 7)