Revert file transactions in reverse order.

Revert in the reverse order in which the transactions were originally
performed.
Merge pull request #24 from modocache/hotfix-transaction-revert-order

Revert file transactions in reverse order.
Fix url template tags for Django 1.5 support
Add context_keys to TemplatesGenerator for Django 1.5 support

MODEL_NAME_archive_year.html uses 'year' the context of YearArchiveView.

But, on Django 1.5, it is returned as a date object.

So the template must use 'year.year'.

In order to maintain backward compatibility, add context_keys and
set proper key depending on the version of Django.
Merge pull request #27 from drillbits/django-1.5-support

Django 1.5 support
2to3
python3-ism
Update.