Change Virtus::Equalizer behaviour to be closer to equalizer

* Even though the implementations differ I wanted to bring the
  behaviour closer inline to equalizer so that when we do factor
  the code out it shouldn't change behaviour from the pov of the end
  user.

  The remaining change will be to add coercion in #==, but early
  attempts to add it caused other spec failures, so I wanted to
  commit what I have now since it is working.
Add yard group to the list of Gemfile groups bundler should skip