Updated the download example script with latest checklist_scrapers settings.
Added pytz to requirements.
Updated datetimes so they are timezone aware.
Dates are now derived from timezone aware datetimes.

Replaced calls to datetime.date.today() with ones to
django.utils.timezone.now().date() so dates, particularly for the
date a checklist was added to the database reflects correctly the
database server date.
Merge branch 'timezones' into develop
Updated changelog with changes made for timezones.
FACTORY_DJANGO_GET_OR_CREATE is now used only for reference data.

Previously it was used on Location which created problems in a test
on an application that used checklists where two different locations
with the same name but from different regions (a common situation)
resulted in only one object being created instead of two.

Add the setting to SpeciesFactory since that is also reference data.
load_checklists now deletes files.

When a checklist is loaded successfully the load_checklists management
command now deletes the file containing the JSON data. This ensures
that the downloads directory does not fill up with files over time.

If there was an error loading the checklist then the file is left alone.
That allows another attempt at loading later. If the file is no longer
available from the source (eBird only provides data for up to the last
30 days) then keeping the file either allows the problem to be fixed,
for example if there was some piece of reference data missing from the
database or the file can be used for debugging.
Merge branch 'doc-updates' into develop
Updated version number for release
Merge branch 'release-0.4.5' into develop