store translations for unavailable locales if enforce_available_locales is false

[wjordan]

Fixes issue described in #404 where the enforce_available_locales setting is not respected by the optimization added in #391.

Adds I18n.enforce_available_locales && to the early-exit conditional in #store_translations, so that translations for locales not in the available_locales array will not be stored only if enforce_available_locales is set to true.

Updated tests to reflect changed behavior.

[radar]

I've investigated #404 and can confirm that there's still an issue in 0.9.4. Your wonderful steps to reproduce worked a treat. I checked out to this branch locally and it does indeed fix the issue. The code + tests are great too.

Just re-running build 529.10. It failed for what appeared to be a glitch-y reason. Once that passes, I'm happy to merge this and to release 0.9.5 with this fix.

Thanks for your work @wjordan! ❤️

[btrd]

Is it possible to release this fix in a 0.9.6 version ?

Rails (in the last version 5.1.5) require ~> 0.7 so it is not possible to have this fix in a Rails project.

I think it would make sense to have a 0.9.6 versions.

[radar]

@btrd I am not sure what you mean. The merge commit for this PR shows that the commit is in the v0.9.5 and the v1.0.0 branch.

I just installed a new Rails 5.1.5 app locally and it is using i18n v0.9.5 which contains this fix. Why would I need to do a v0.9.6 release, if v0.9.5 already includes this fix and is used by default in new Rails applications?