Bump version to 3.7.0 to reflect change in card.io functionality.
Bump version to 3.7.0 to reflect change in card.io functionality.

- Include SSL Pinning code refactor.

apascual/braintree_ios,bytemarkinc/braintree_ios,EverettQuebral/braintree_ios,TeachersPayTeachers/braintree_ios,billCTG/braintree_ios,EverettQuebral/braintree_ios,braintree/braintree_ios,apascual/braintree_ios,billCTG/braintree_ios,billCTG/braintree_ios,apascual/braintree_ios,TeachersPayTeachers/braintree_ios,EverettQuebral/braintree_ios,braintree/braintree_ios,billCTG/braintree_ios,bytemarkinc/braintree_ios,braintree/braintree_ios,EverettQuebral/braintree_ios,braintree/braintree_ios,EverettQuebral/braintree_ios,Feverup/braintree_ios,bytemarkinc/braintree_ios,billCTG/braintree_ios,Feverup/braintree_ios,Feverup/braintree_ios,bytemarkinc/braintree_ios,apascual/braintree_ios,Feverup/braintree_ios,bytemarkinc/braintree_ios,TeachersPayTeachers/braintree_ios,TeachersPayTeachers/braintree_ios,TeachersPayTeachers/braintree_ios