Now with Linux support!

The figure will be copied to the clipboard as a PNG, regardless of matplotlib.rcParams['savefig.format'].
Requires either Qt or GTK libraries for clipboard interaction. Automatically detects which is being used from matplotlib.get_backend().
- Qt support requires PyQt5 or PySide2.
- GTK support requires pycairo, PyGObject and PIL/pillow to be installed.
- While Qt and GTK are both supported, they each have different requirements. As such, those requirements will not be automatically installed along with the addcopyfighandler module.

Improved application compatibility on Windows (optionally uses Pillow)

If Pillow is installed, all non-SVG format specifiers will be overridden and the figure will be copied to the clipboard as a Device-Independant Bitmap.
If Pillow is not installed, the supported format specifiers are 'png', 'jpg', 'jpeg' and 'svg'. All other format specifiers will be overridden and the figure will be copied to the clipboard as PNG data.

If matplotlib.rcParams['savefig.format'] is 'svg', the figure will be copied to the clipboard as an SVG.
Alas, SVG output is not currently supported on Linux. Pull requests that enable SVG support there would be welcomed.