Updated ATOM feed partials to use markdown instead of simple_format.

app/views/events/_event_issue.atom.haml

 %div{:xmlns => "http://www.w3.org/1999/xhtml"}
-  %p= simple_format issue.description
+  %p= markdown issue.description

app/views/events/_event_merge_request.atom.haml

 %div{xmlns: "http://www.w3.org/1999/xhtml"}
-  %p= simple_format merge_request.description
+  %p= markdown merge_request.description

app/views/events/_event_note.atom.haml

 %div{:xmlns => "http://www.w3.org/1999/xhtml"}
-  %p= simple_format note.note
+  %p= markdown note.note

app/views/events/_event_push.atom.haml

@@ -6,7 +6,7 @@
       %i
         at
         = commit[:timestamp].to_time.to_s(:short)
-    %blockquote= simple_format(escape_once(commit[:message]))
+    %blockquote= markdown(escape_once(commit[:message]))
   - if event.commits_count > 15
     %p
       %i