Show deleted shipping methods for shipping rates

Fixes #4328
Correct Rails version in readme
Bump Spree master to 2.2.1

Master should be higher then the latest stable branch.
Fixes incorrect order.item_total when line items have multiple currencies

Provides protection against order/line_item currency mismatch
Move currency update logic into it's own concern.
Bump to 2.3.0.beta
Remove unused api/lib/spree/api/version.rb
Bump Paperclip to 4.1.1