Add bin, card_type, last_4, and unique_number_identifier to credit cards.
Merge remote-tracking branch 'brandon-beacher/add_more_fields_to_credit_cards'

* brandon-beacher/add_more_fields_to_credit_cards:
  Add bin, card_type, last_4, and unique_number_identifier to credit cards.

Conflicts:
	lib/fake_braintree/credit_card.rb