Log Message:
Update ruby-i18n to 0.8.6.

v0.8.5							2017/07/10

* Improved error message for MissingPluralizationKey error - See #371
* Fixed a thread issue when calling translate when fallbacks were enabled -
  See #369

v0.8.6							2017/07/10

* Fixed a small regression introduced in v0.8.5 when using fallbacks - See
  #378