Ensure tests do what they are supposed to

Feature tests were not running appropriately. The tests in dummy test app that aruba creates in `tmp/aruba/testapp` were failing if triggered manually. This was due to the original bundler session being shared within the cucumber tests. I ended up using an `Around` hook to wrap the scenarios in a `Bundler.with_clean_env` block. This allowed the tests to run with their own bundler environment.