0.2.0

• Added option to exclude_locked_layers from the exported track.
• Added sample_rate and channels settings to the render_audio() function.
• Transformed sounds are no longer held in memory all at once, dramatically reducing memory usage while exporting a track.
• Fixed a MemoryError occurring when exporting songs with a lot of notes.
• Fixed a bug in song length calculation on NBS versions 1 and 2.