Removes association
Removes bill_address association
Adds bill and ship address methods back into the extension
Billing address is mandatory
Merge pull request #8 from DynamoMTL/fix/bill-address-validation

Billing address is mandatory
Merge branch 'master' into feature/subscription-preorder

* master:
  Billing address is mandatory
  Adds bill and ship address methods back into the extension
  Removes bill_address association
  Removes association

Conflicts:
	app/models/spree/subscription.rb