Django Timezone

[camflan]

Updated to use django.utils.timezone

[coveralls]

Coverage increased (+14.5%) to 100.0% when pulling c81774a on camflan:master into 6bad475 on arteria:master.

[camflan]

This is ready for review @jvamvas @philippeowagner,

I think I handled timezones properly, trying only to convert to a location timezone where necessary for comparison.

[camflan]

Actually, I don't think I tackled this correctly. Ideally, we wouldn't override timezone.activate that might be set elsewhere in the codebase.

I've been thinking about how to properly fix it, and I think there are 2 possible ways:

1. make OpeningHour boundaries aware by setting TZ on the datetime.time instances before they are saved to TimeField. Then we could use the aware (UTC) instances that timezone.now returns for comparisons.
2. require passing location to get_now so we can create a location-local naive datetime for us to use for comparisons.

I think 1 is probably the best.

Also, can we get rid of the code in get_now that reaches into the request? I can't find anywhere that it's being used, and it would simplify that quite a bit.