Enabled Python 3 compatibility, and changed tabs to spaces to prevent errors.
Fix importing of Queue module
Bug fixes for running under Python 3.

	modified:   ginga/PythonImage.py
	modified:   ginga/gtkw/plugins/Thumbs.py
	modified:   ginga/misc/Bunch.py
	modified:   ginga/qtw/plugins/Thumbs.py
	modified:   scripts/example2_qt.py