basic feature

Requires set of ENV['BUNDLE_GEMFILE'] if run with bundle exec, otherwise not. Only seems to check the student archive, and not combine the standard solution with it first, so using a full app in that tar.gz file appears to work.
Copied same code to spec to demonstrate same needs if run with rspec or cucumber.

Backed off the refactoring, copy-pasted, etc. to make this a minimal set of changes for demonstration, communication.