title: Case Insensitive default_scope :order?
body: <p>I have the following test that passed under mysql (using FactoryGirl):</p>
  
  <pre><code>  test "order by title" do
      @library = create(:drawing_library, title: 'Accessories')
      @drawing = create(:drawing, drawing_library: @library, title: 'Test Drawing')
      create(:drawing, drawing_library: @library, title: 'z')
      create(:drawing, drawing_library: @library, title: 'm')
      create(:drawing, drawing_library: @library, title: 'b')
  
      str = ''
      @library.drawings.each do |dwg|
        str += dwg.title
      end
  
      assert_equal 'bmTest Drawingz', str
    end
  </code></pre>
  
  <p>The Drawing model is:</p>
  
  <pre><code>class Drawing &lt; ActiveRecord::Base
    belongs_to :drawing_library
    default_scope order: :title
    ..
  end
  </code></pre>
  
  <p>Under postgresql, this test now fails with:</p>
  
  <pre><code>&lt;"bmTest Drawingz"&gt; expected but was
  &lt;"Test Drawingbmz"&gt;.
  </code></pre>
  
  <p>This appears to be because of the T in 'Test Drawing' being uppercase.  If I change it to 'test Drawing', the test passes.</p>
  
  <p>Is there a way to make <code>default_scope order</code> case insensitive?</p>