v2.1.0
Changes:
- added automated detection of png image types through read of PNG file signatures (issue #45)
- removed testing for *.png file extension to process files (issue #45)
- added support for simple modification of pnquant and zopflipng paths that are used for optimization, convert to system PATH installed versions by modification of the Python script (issue #40)
- bugfix for macOS GUI and right-click menu service failures with absolute file paths that contain multiple directory levels with space characters (issue #47)