struct_time to datetime conversion.
Add safety check for start dates unbound
Coding consistency changes for code review.
Minor code review fixes (removing commented code).
Make pymongo tz_aware
Added date_util tests back in and handle null time obj.
Move tz_aware into connection config rather than settings.
Make django use_tz
Fixed use_tz not being effective in cms
Partial implementation of means to get xmodule from descriptor and
attempt to test xmodule_modified (see fixme)
Removed obsolete else clause from before conversion
Ensure factories use datetime not struct_time for start date
Added more unit tests for settings encoder
Test all date_utils variants
Revert bad merge