celery: simplify internal configuration and app creation We used celery.app.app_or_default() which creates a "global fallback app instance" which relies on the CELERY_LOADER environment variable to load the configuration. That worked but was messy. Instead, do something more like described in http://docs.celeryproject.org/en/3.1/userguide/application.html where the app is a celery.Celery() instance and configuration is loaded explicitly by its config_from_object method. Using config_from_object we don't need explicit invocation of import_default_modules and can take pass PylonsSettingsProxy directly, leaving PylonsLoader unused and removed. Modified by Mads Kiilerich.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.