[api] Added a CheckoutsController
- Allows creation of a new, empty order
- Can transition an order from cart to complete state
- Removed now unneeded address and delivery actions from API's
  OrdersController
[api] Added support for updating an order's payments using CheckoutsController
Reject instead of deleting months from the localization list

The %B date formatting operator relies on nil for the first month
in the month_names array. Deleting it from I18n will cause month
shifting

Fixes #2427
Correction of the problem that a newline is added to by google chrome browser

Fixes #2447
sort en.yml

Fixes #2446
Correct factory used in product_attributes for shared "product prototype" context

Fixes broken build: https://travis-ci.org/spree/spree/jobs/4244803
Cleanup product and variant factories

Fixes #2419
Freeze to jquery-rails 2.1.4 as jQuery 1.9 breaks a plugin