fix(travis): add email settings
feat(heroku): adjustments for Heroku deployment
fix(travis): remove nodeenv
feat(staticfiles): add S3 support
feat(runtime): Change runtime to 2.7.8

django-storages do not support Python 3, as we're dependent on it
the current Heroku runtime is downgraded to Python 2.7.8

Issue: http://code.larlet.fr/django-storages/issue/155/python-3-support
fix(readme): add warning regarding S3 support and Python 3