#818 Remove mopidy lux from documentation

(cherry picked from commit 06d7d650f870dfe55e02bc091f6f344df2762ef9)
(cherry picked from commit c230a0f64cf48eac18d72dc04827afe88220bcc6)
docs: Add sponsors page

(cherry picked from commit b40409141fe6b8012ff11bb2d9fb041831e02571)
Merge branch 'master' of https://github.com/mopidy/mopidy into playback-history
Switched track name and artist order in history object.
Use assertIn instead of assertTrue to test membership.