Refactor Dependency to models
Reify Repo Cookbook concept

RepoCookbook holds information about a specific cookbook on Repository
Manager.
Blacklist metadata.rb's fields instead of using a whitelist

This is required in order to parse correctly metadata containing things
like:
  %w{ cookbook1 cookbook2 }.each do |cb|
    depends cb
  end
Use GitHub token for every spec and use kitchen-inspector user