Start on translation

* Add fab commands to update message files
* Go through, marking English text for translation in Python and
  templates.
Refs #163: Expose category on lightning talk proposals
Don't redirect forever if the registration URL has not been configured
Refs #169: Remove proposal slide_deck field
Fix pycon-aid email address
Merge branch 'develop' into feature/translation-process

Conflicts:
	symposion/templates/registration/login.html
Merge branch 'feature/translation-process' into develop
Merge branch 'feature/169-remove-proposal-slide-deck-field' into develop

Conflicts:
	pycon/models.py
Merge branch 'feature/163-lightning-talk-categories' into develop
Merge branch 'develop' into staging