Integration tests are useful in detecting breakages but much slower so
let's only use one per command and install formula outside the
integration test framework (which is also slow).
Rather than trying to be smart and doing this ourselves in `brew cleanup` let’s just installed Bundler somewhere it doesn’t try to clean itself up and use `bundle install --cleanup` when we need cleanup done.
Also, use `ohai` and `odie` when possible as they look nicer.
