title: How can I get all list of scopes in ActiveRecord 3.x
body: <p>I am using ActiveRecord with Rails 3.</p>
  
  <p>I defined scopes in my model. How can I get the list of all scopes of that model?</p>
  
  <p>Previously I could use <code>Model.scopes</code></p>
  
  <p>OR
  Can I check a scope is defined or not? Something like <code>Model.scope_defined?("scope_name")</code></p>
  
  <p>Thanks in advance.</p>