docs: Update Travis badge URL
session: remembered_user{ => _name}

For consistency with return type and session.user_name.
session: Add flush_caches()
utils: Test to_bytes() corner cases
utils: Make to_unicode() handle more corner cases
session: Add connection_state property
session: Add set_cache_size()
session: Add player_seek()
session: Test player_play() error case
session: Add player_unload()
docs: Add new classes
session: Add player_prefetch()
session: Add playlist_container attribute
session: Add inbox attribute
session: Add starred attribute
session: Add starred_for_user()
user: Add starred attribute

A convenience wrapper around session.starred_for_user(user.canonical_name).
fab: Turn on branch coverage