pkg: Include tox.ini, explicitly prune empty docs and fonts dir

MANIFEST.in

@@ -5,5 +5,9 @@ include MANIFEST.in
 include README.rst
 include mopidy_touchscreen/ext.conf
 include mopidy_touchscreen/icomoon.ttf
+include tox.ini
 
 recursive-include tests *.py
+
+prune docs
+prune mopidy_touchscreen/fonts