Add index to Spree::User.spree_api_key

Fixes #3884
Updated docstring explaining how to include controller requests test support in rspec.

Fixes #3898
Dont lazy load variants in Shipment `manifest`

Rails 4.0.1 fixes an issue where `default_scope` would not be applied to
`joins` association, see https://github.com/rails/rails/commit/b407839601c8dc7b007a6baddea3696b737c352b
(I liked that bug pretty much myself). Side effect is users upgrading to
Rails 4.0.1 would see errors when displaying orders with deleted variants
Fixed Spree::Api::ProductsController#index to accept multiple ids

Fixes #3886
Relax money dependency
Bugfix: Taxons could not be ordered

If you reorder the taxons in the admin interface, it does not
have any effect, because the ordering of the taxons is not
used. Setting a default scope with this ordering fixes that.

Fixes #3891
Fixes #3833
Fixes #3390
Spree::Payment.class.undescore will always convert spree/payment

Fixes #3889

Conflicts:
	backend/app/views/spree/admin/payments/show.html.erb

Conflicts:
	backend/app/views/spree/admin/payments/show.html.erb
Fix fieldset not resizing on some @media sizes.

Fixes #3871
Fixes #3890
[api] Don't depend on ordering in taxons_controller_spec
Remove console.log from taxon autocomplete
Check for presence in Spree::CreditCard#expiry method

The expiry method needs to check for presence before parsing. An empty card expiration field will raise the error "no implicit conversion of nil into String" on submission.

Fixes #3847
Fixes #3896
Use correct default_scope syntax for Rails 4 in Taxon
Move script/rails to bin/rails in extension generator. Fixes #3904
Clear out entries from CHANGELOGs
Use actual assertions in credit_card_spec
CreditCard#expiry=: Only prefix '20' to year if 2-digit year is specified
Use evaluate_script instead of execute_script

evaluate_script was meant to be used for these kinds of situations.

Fixes #3894
Clarify how spree accepts pull requests, may need to be cross committed to the docs in spree-guides is support for the change is present.

Discussed in #3894
Specify class name for users association in Promotion::Rules::User
Update option_type for has_many product through

Needed for search from option value.

Fixes #3910