UI changes:

* .page_title  class added. Used for better page headers
* improved help page
* added back links for help pages
* show app version & revision on help page

Backend changes:
* Gitab::Version && Gitlab::Revision constants

app/views/help/workflow.html.haml

@@ -1,5 +1,8 @@
 - bash_lexer = Pygments::Lexer[:bash]
 %h3 Workflow
+.back_link
+  = link_to help_path do 
+    ← to index
 %hr
 
 %ol.help