Allow SSL callbacks from all providers

Fixes #99
Add ssl module.
Update path_prefix default to match the old default

The old route was /users/auth/:provider and this has changed the default to /user/auth/:provider
I believe the default should not break existing apps that were relying on that route

Fixes #103
I think we can remove this README notice now
Spanish mx translations

* Internationalize hardcoded messages for:
  - OmniauthCallbacks
  - UserAuthentication

* Add es-MX translations

Fixes #108
Merge branch 'spree_2-0-stable' into 2-0-stable

# By Ryan Bigg (2) and others
# Via Ryan Bigg
* spree_2-0-stable:
  Spanish mx translations
  I think we can remove this README notice now
  Update path_prefix default to match the old default
  Add ssl module.
  Allow SSL callbacks from all providers