Update CHANGELOG for 4.9.4
Update CHANGELOG for 4.9.4

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