RSpec can't stub methods

In order to allow rspec to stub methods,  respond_to? need the complete signature.

you can reproduce this staff with
    before do
      allow(Desk).to receive(:update_case)
    end

I also removed ruby-debug from spec/helper.rb (it's not a gem dependency, moreover i used ruby 2.1.2 and it doens't support it very easily).


If you'll accept this pull request, please let me know when you publish on rubygems, so i can fix the Gemfile