[Test] Add test16_mod_key
[Test] Add scroll key test
[Test] Add wrapper function for popup.show_caption()
[Test] Cleanup
Firefox ESR 17 support
[Test] Wrap BytesIO in util.py
[Test] Add test17_mark_visited
[Test] Python2 support
Change version number 1.7.2 => 1.8.0
Update README, changelog