Update Ansible formula to 1.6.6

I went off the changes from https://github.com/Homebrew/homebrew/pull/30492 and this wiki doc: https://github.com/Homebrew/homebrew/wiki/Formula-Cookbook

1.6.6 is a security release, here's a diff: https://github.com/ansible/ansible/compare/v1.6.5...v1.6.6