Remove old shell provision file
Switch provisioning to use basic Ansible playbook

* Modify Vagrantfile to use Ansible provisioning
* Add basic playbook
* Add ansible_hosts
Switch to Ansible for provisioning

* Reasonably proper Ansible tasks for Node.js, Pandoc, rbenv, Ruby and Bundler
* Remove `ruby18_source_location` from Gemfile and Gemfile.lock (no longer necessary)
* Update README.md to reflect

Fixes #9
Merge branch 'feature/ansible-provisioning' into develop

Fixes #9 even more.