Merge tag 'v1.3.1'

Conflicts:
	ChangeLog
	bingo/locale/de/LC_MESSAGES/django.po
	bingo/views.py
	setup.py
pep8 fixes
updated copyright for the new year
check if field2word data from cache is consistent, refresh from db if not.
recalculate vote counts, when a word is not in the cached dict
doc update (vote cache), pep8 fix
reload the bingo page when game is expired

if the javascript is still polling for new votes after the game is
expired, the page reloads, so it stops polling.
update the last_used timestamp with .update() instead of .save()
use now() with timezone support
performance: select list of games only once
style: no clearfix after theme chooser.
AUTHORS: mention both years
fix: always return a HttpResponse in change_theme

redirect to main page, even if the form is invalid or the view is called
without POST parameters.
fix: updating the timestamp of new games works now
last_used is now auto_now_add and updated via .update()

now last_used is NOT updated when a Game/BingoBoard is edited.
This is needed for adding Game descriptions after the Game is finished.
migration: unique_together of game_id and board_id removed, auto_now_add for last_used fields

- unique_together of game_id and board_id is now checked in .save(),
  because it depends on the Site, too.
- last_used is auto_now_add and updated via .update(), because editing
  Game / BingoBoard objects in the admin interface should not change the
  timestamp.