v2.0.0

Highlights:
1. Add support for macOS 10.15 new permission politics.
Please view the electron example (run npm start at project root dir) to see how to use this.
2. Better support for debug.
Right now the stderr will provide verbosely information about how the colorpicker is running.
The developers can use this log if something bad happened, which is very unlikely.

If you have any question, please don't hesitate to contact me.