Temporarily hide Travis badge
Temporarily hide Travis badge

The Travis builds have been problematic for a while, and this badge
gives a misleading status of the test story.  The project is tested
locally instead, and hiding the badge should not convey that any PRs
should not include tests, they absolutely will need them to be
considered.

braintree/braintree_ios,braintree/braintree_ios,braintree/braintree_ios,braintree/braintree_ios