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
Refer to Spree.user_class always for Spree::Promotion::Rules::User

Conflicts:
	core/app/models/spree/promotion/rules/user.rb
[backend] Add empty partial for free shipping action
Update option_type for has_many product through

Needed for search from option value.

Fixes #3910
Added Kaminari call to add rel next/prev to head

Fixes #3903
Persist search fields across requests for sales total report

Fixes #3906
Make product variants thumbnails selection more specific in JS
Use poltergeist for frontend build
Sorts country list correctly with accents

Fixes #3911
[frontend] Wait a couple of seconds in address_spec for poltergeist to catch up with latest changes
Wait until jQuery AJAX requests complete before checking page