Install the latest version of bash (4.3)
Link /bin/bash to /usr/local/bin/bash

On RHEL, /bin is before /usr/local/bin, so simply shelling out to
`bash` results in the incorrect bash being used.
Change ruby_install `action :run` to `action :install`
Don't permit setting a default system Ruby

Turns out, setting the Ruby fucks things up for Test Kitchen and every
future CCR will fail because "the Ruby" is the one you set, not Chef's.
Apparently there's some tooling that just shells out to `chef-client`
instead of `/opt/chef/embedded/bin/chef-client`... But hey, what is
software engineering if we don't make shitty decisions, amirite?
Don't install bash until after platform-specific things are done

This permits software (cough Debian) to be update to date (cough apt-
cache).
Add minimal ChefSpec testing