* Simplify language chooser
- Allows usage of i18n_patterns with prefix_default_language=False
- Change templatetag from simple tag to an inclusion tag
- Reduces complexity by relying on Django's behavior in the
set_language view: it will translate any url passed as 'next'.
This behavior has been present since Django 1.9.
- Remove individual forms for each language
Fixes#327
Reference: aa5ab114e3
* Add check to ensure LocaleMiddleware
* Remove check in favor of silent warning
* Fix template tag tests
b393c11ecb