Ability to export song as a collection of track files (midi) and a single audio comped audio file.
So for ex:
If loop has 3 tracks then export should be a zip file containing:
- 3 separate midi files
- 1 audio file
- User should be able to export to dest using iOS standard picker or email
Diagram
![Export Song](https://camo.githubusercontent.com/e97a013ed5fc6dec39b4bead174037d6ee1d0c8697eca629a27ef97cae5e4a63/68747470733a2f2f646f63732e676f6f676c652e636f6d2f64726177696e67732f642f315a3051764f3544494555567057475a547541584a4c2d686b45494f304e2d306656344c6f5f626c49614e382f7075623f773d39363026683d373230)