Package leo-editor as a macOS .app bundle

[Shakeeb]

In case anyone's interested I've just posted a proof-of-concept script to package a minimal cut of leo (only standard plugins for now) as a standalone macOS .app bundle using Ronal Oussoren's fantastic py2app.

This came out of a recent fruitful discussion with Thomas Passin on the leo GitHub tracker.

I've put the script to automatically build it via a virtualenv in a repo https://github.com/shakfu/leo-app-builder for further iterations.

The script can also be found in the issue linked above. 

A big caveat: it's fresh off the oven and pretty much untested beyond a few successful runs..

S