Add extra decision-tree translations.

By looking at the list here:
https://github.com/zooniverse/Galaxy-Zoo/blob/master/app/views/navigation.eco#L36-L46
and guessing the URI like so:
http://www.galaxyzoo.org/locales/LOCALE.json
as suggested here:
https://github.com/zooniverse/Galaxy-Zoo/commit/cf694a24d23989b3fb2432adb314d0b354b8a81a

These are under the Apache 2 license:
https://github.com/zooniverse/Galaxy-Zoo/commit/0a54404f8fe3282bbea349d9a2075ee310c5ac01