New formula: Ansible

Configuration management and IT orchestration tool.

This is a Python package that is published to PyPI, but its installation is broken with Homebrew `pip` because of hardcoded paths. In discussions about fixing standard Python installation mechanisms, the maintainer [has stated pretty resolutely][1] that he wants it to be considered an application and not a Python library/package. It is also in MacPorts.

I first did this with a less brute-force approach that requires a two-line patch, but it leaves the user to add a config file to change an essential default path, and it leaves incorrect paths indicated in man pages, etc. So I've ended up doing [exactly what MacPorts does][2].

/cc @mpdehaan

[1]: https://groups.google.com/forum/#!topic/ansible-project/eEZ968npkDw/discussion
[2]: https://trac.macports.org/browser/trunk/dports/sysutils/ansible/Portfile