advance develop past 1.1.0
add list tracks for music manager; fix bug in protocol merge
add mm.download_song
check response codes
fix mm.download_song docstring
don't wrap HTTPError trace
retry mm song download test
better error logging; retry defaults to (AssertionError, CallFailure)
add mm list/download to docs
note possibility of encoding errors in download_song
properly generate mac string, and verify format when user-provided
properly generate mac string, and verify format when user-provided
update docs
Merge branch 'develop' of github.com:simon-weber/Unofficial-Google-Music-API into develop
move mac formatting/checking to utils
make create_mac_string more robust
actually make cms robust (trim trailing L)
add (optional) token field to GetPlaylistSongs (close #122)
add albumPlaybackTimestamp (close #123)
doc fixes