mido-ports now prints port names in single ticks.
bugfix: tempo changes caused timing problems in MIDI file playback.

(Reported by Michelle Thompson.)
Renamed _compute_seconds_per_tick() to _get_seconds_per_tick().
Bugfix: MidiFile.length was computed incorrectly.
MidiFile.__iter__() now yields end_of_track messages.
Moved _merge_tracks() out of MidiFile. Possibly exposing it at some point.
Bumped version to 1.1.10.