Ansible setup.sh

Moves setup.sh dependency provisioning to Ansible.

Replaces the error-prone bash script provisioning in OS X and Linux
with an Ansible playbook, which has clearer error messages/handling,
and will hopefully be more reproducible across machines.

r=@kovach,@fnoble,@cbeighley

Closes #130.
Closes #146. 
Closes #147.

<!---
@huboard:{"order":144.5,"milestone_order":155.0,"custom_state":""}
-->