Update CHANGELOG for 4.3.0
Update CHANGELOG for 4.3.0

apascual/braintree_ios,billCTG/braintree_ios,Feverup/braintree_ios,billCTG/braintree_ios,Feverup/braintree_ios,billCTG/braintree_ios,braintree/braintree_ios,Feverup/braintree_ios,billCTG/braintree_ios,billCTG/braintree_ios,apascual/braintree_ios,apascual/braintree_ios,braintree/braintree_ios,Feverup/braintree_ios,braintree/braintree_ios,braintree/braintree_ios,apascual/braintree_ios