Refresh the plugin to the current scribes.

* fix `setup.py` to actually install plugin in the proper place
  (~/.config/scribes/LanguagePlugins)
* change activation shortcuts to <ctrl><alt>j and <alt><shift>r which
  are not conflicting with the default scribes shortcuts.
* remove trailing spaces

Signed-off-by: Matěj Cepl <mcepl@redhat.com>