adds Assembly badge to the footer

For Coderwall bounty #545

Author: than

app/views/shared/_footer.html.haml

@@ -14,7 +14,9 @@
         %li= link_to('Jobs',                '/jobs')
         %li.employers= link_to('Employers', employers_path)
         =yield :footer_menu
-
+      
+      %ul.assembly-badge
+        %li <a href='https://assembly.com/coderwall?utm_campaign=assemblage&utm_source=coderwall&utm_medium=flair_widget&utm_content=flag_with_text'><img src='https://treasure.assembly.com/assets/badges/flag_text-6cfc91728f9f0090d1688e4f0d41a639.svg' width=243px height=41px /></a>
       %ul.copyright
         %li Copyright &copy; 2015 Assembly Made, Inc. All rights reserved.
       %ul.credits