Add test helper for checking a user's language.
Add tests for LanguageChoice.
Fix bug in saving language from LanguageChoice state.
Add custom assert message for check.user.lang.
Add tests for check.user.lang.
Remove stray .only.
Merge branch 'feature/issue-87-test-language-choice-state' into develop
Merge branch 'develop' into feature/issue-23-reduce-api-setup-boilerplate