added test for left and top

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    compass (0.11.beta.2.995a20c)
+    compass (0.11.beta.2.153582f)
       chunky_png (~> 0.12.0)
       sass (>= 3.1.0.alpha.218)
 

spec/compass/sass_extensions/sprites/image_spec.rb

@@ -22,6 +22,8 @@ describe Compass::SassExtensions::Sprites::Image do
     its(:width) { should == 10 }
     its(:height) { should == 10 }
     its(:digest) { should == digest }
+    its(:top) { should == 0 }
+    its(:left) { should == 0 }
   end
 
   let(:options) {