title: Rails Validates less than 0 or greater than 0, or field not equal to 0
body: <p>I've added validation to my Rails model for <code>less_than</code> and <code>greater_than</code>, but they obviously conflict each other.</p>
  
  <p>I want to make sure Rails validates a field on model to never be 0.  So less than OR greater than 0, but not both because that's not possible.</p>
  
  <p>How can I do this?</p>