1. Now if request.META.DJANGO_DEBUG is set, writing the word DEBUG in the middle of the page, to make it conspicuous.
Removed HTML code that was ignored anyway (not in any django block, given that we are extending another template).
Major changes: detect debug vs. production, and act accordingly.

1. Now detecting RUNNING_DEV_SERVER, and setting DEBUG to the same thing.
2. If we are in production, getting SECRET_KEY from an environment variable. Otherwise doing lots of checks to ensure we are not on Heroku (in production) by some accident.
3. Specifically, detecting the system timezone and saving it in the ORIGINAL_TIMEZONE environment variable. (Need to do that because Django will load settings.py more than once, and the second time the system timezone will already be changed to what we requested in settings.TIMEZONE). If the original timezone is UTC/GMT, chances are that we are in production, so don't run if DEBUG is True.
4. Also, if we are in DEBUG, set the environment variable DJANGO_DEBUG to 1, so that templates can indicate when we are in debug.
5. Automatically using Heroku's postgresql or mysqlite, depending on whether we are in debug or in production.
6. Only enabling security (SSL, HSTS, etc.) when in production.