patched image functions to accept a real path

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    compass (0.12.0.alpha.0.8c48248)
+    compass (0.12.0.alpha.0.ec7c4b2)
       chunky_png (~> 1.2)
       fssm (>= 0.2.7)
       sass (~> 3.1)

lib/compass/sass_extensions/functions/image_size.rb

@@ -1,14 +1,22 @@
 module Compass::SassExtensions::Functions::ImageSize
   # Returns the width of the image relative to the images directory
   def image_width(image_file)
-    image_path = real_path(image_file)
+    image_path = if File.exists?(image_file.value)
+      image_file.value
+    else
+      real_path(image_file)
+    end
     width = ImageProperties.new(image_path).size.first
     Sass::Script::Number.new(width,["px"])
   end
 
   # Returns the height of the image relative to the images directory
   def image_height(image_file)
-    image_path = real_path(image_file)
+    image_path = if File.exists?(image_file.value)
+      image_file.value
+    else
+      real_path(image_file)
+    end
     height = ImageProperties.new(image_path).size.last
     Sass::Script::Number.new(height, ["px"])
   end

lib/compass/sass_extensions/functions/sprites.rb

@@ -61,7 +61,7 @@ def sprite_file(map, sprite)
     verify_map(map, "sprite")
     verify_sprite(sprite)
     if image = map.image_for(sprite.value)
-      Sass::Script::String.new(image.relative_file)
+      Sass::Script::String.new(image.file)
     else
       missing_image!(map, sprite)
     end