title: Switch to Ruby 2.3.0 (from 2.0.0) creates issue on Active Record validates
body: <p>I recently switched my Rails 4.2 app from ruby 2.0.0 to 2.3.0 and when I start my rails server ($ rails s), a new notifcation just appeared</p>
  
  <pre><code>/home/app/models/user.rb:127: warning: key :numericality is duplicated and overwritten on line 128
  /homeapp/models/user.rb:127: warning: key :on is duplicated and overwritten on line 128
  /home/app/admin/user.rb:142: warning: key :collection is duplicated and overwritten on line 147
  /home/app/models/deal.rb:223: warning: key :numericality is duplicated and overwritten on line 226
  /home/app/models/deal.rb:234: warning: key :numericality is duplicated and overwritten on line 237
  </code></pre>
  
  <p>Here is an example of the line causing issues, they are the ones where on creation of the account I set the attribute nb equal to 3 (on: :create), and the user, in the life of his account, can grow his number of permissions but will never be able to have more than 7 (on: :update).</p>
  
  <pre><code>validates :nb_of_permissions,
              presence:true,
              numericality: { equal_to: 3 }, on: :create,               
              numericality: { less_than_or_equal_to: 7 }, on: :update   
  </code></pre>
  
  <p>What should I change ?</p>
  
  <p>Thanks</p>