Added +sticky-footer mixin

Forces page layout to expand, pinning the footer
to the bottom edge of the browser window.

Refer to:
http://ryanfait.com/resources/footer-stick-to-bottom-of-page/

Manifest

@@ -38,8 +38,10 @@ examples/blueprint_semantic/stylesheets/liquid.sass
 examples/blueprint_semantic/stylesheets/print.sass
 examples/blueprint_semantic/stylesheets/screen.sass
 examples/compass/compass.html
+examples/compass/sticky_footer.html.haml
 examples/compass/stylesheets/compass.sass
 examples/compass/stylesheets/images/blue_arrow.gif
+examples/compass/stylesheets/sticky_footer.sass
 examples/compass/stylesheets/utilities.sass
 examples/compass/utilities.html.haml
 examples/yui/divisions.html.haml
@@ -70,8 +72,10 @@ frameworks/blueprint/templates/project/ie.sass
 frameworks/blueprint/templates/project/print.sass
 frameworks/blueprint/templates/project/screen.sass
 frameworks/compass/stylesheets/_compass.sass
+frameworks/compass/stylesheets/compass/_layout.sass
 frameworks/compass/stylesheets/compass/_reset.sass
 frameworks/compass/stylesheets/compass/_utilities.sass
+frameworks/compass/stylesheets/compass/layout/_sticky_footer.sass
 frameworks/compass/stylesheets/compass/utilities/_general.sass
 frameworks/compass/stylesheets/compass/utilities/_links.sass
 frameworks/compass/stylesheets/compass/utilities/_lists.sass

examples/compass/sticky_footer.html.haml

@@ -0,0 +1,14 @@
+!!! Transitional
+%html{:xmlns => "http://www.w3.org/1999/xhtml", "xml:lang" => "en", :lang => "en"}
+  %head
+    %meta{'http-equiv' => "content-type", :content => "text/html;charset=UTF-8"}
+    %title Compass Sticky Footer Example
+    %link{:rel=>"stylesheet", :href=>"stylesheets/sticky_footer.css", :type=>"text/css", :media=>"screen, projection"}
+  %body
+    #layout
+      #header
+        %h1 Sticky Footer Example
+      This is the main content area.
+      #layout_footer
+    #footer
+      This is the footer area.

examples/compass/stylesheets/sticky_footer.sass

@@ -0,0 +1,12 @@
+@import compass/reset.sass
+@import compass/layout.sass
+
++global-reset
++sticky-footer(72px, "#layout", "#layout_footer", "#footer")
+
+#header
+  :background #999
+  :height 72px
+
+#footer
+  :background #ccc

frameworks/compass/stylesheets/compass/_layout.sass

@@ -0,0 +1 @@
+@import layout/sticky_footer.sass

frameworks/compass/stylesheets/compass/layout/_sticky_footer.sass

@@ -0,0 +1,17 @@
+// Based on http://ryanfait.com/resources/footer-stick-to-bottom-of-page/
+// Mix into the top level.
+// Footer element must be outside of root wrapper element.
+// Footer must be a fixed height.
+
+=sticky-footer(!footer_height, !root_selector = "#root", !root_footer_selector = "#root_footer", !footer_selector = "#footer")
+  html, body
+    :height 100%
+  #{!root_selector}
+    :min-height 100%
+    :margin-bottom= -!footer_height
+    #{!root_footer_selector}
+      :height= !footer_height
+  #{!footer_selector}
+    :clear both
+    :position relative
+    :height= !footer_height