Bump rails to ~> 4.0.5
cancel and void icons should use fa-times
Use fa-check, not fa-ok
Refer to selected shipping rates directly

This means that rates can be available on shipments, but not shipping methods

Useful for extensions like spree_easypost which only set rates and don't have shipping methods
Bump to 2.2.2
Bump to 2.2.3.beta
Refactor Spree::ProductHelper#variant_price_diff

* Change the logic of the code to make it easier for the next
  commit.
* Remove duplicate code from the HTML generation.
Change #variant_price_diff to handle when the product amount is nil
Change #current_order to always lock the order when querying

* I believe some of the problem with the deadlocks is happening because
  of inconsistent locking, and updating without acquiring a lock properly. As a
  test I am going to enable it across the board and see how things perform.
Add inverse_of for more associations involved in cart processing
Add validation to Spree::StockItem for count_on_hand
Change Spree::OrderUpdater#update to be performed inside a transaction