Move submodules to app/lib and appver to settings.
Merge branch 'master' into develop

Conflicts:
	app/.env
	app/lib/ebooklib
	app/lib/pyphen
	app/lib/readability
Merge environment vars with .env settings

The .env file is usually used by Heroku's Foreman to set environment
variables for local runs. We extend this idea and use this same file to
set up the environment in production as well, also on App Engine. This
allows removing common environment variables from app.yaml and
better conformance to DRY.
Merge branch 'develop' to 'master'