Cache readme rendering result

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/helpers/projects_helper.rb

@@ -272,4 +272,8 @@ module ProjectsHelper
       current_user.recent_push(@project.id)
     end
   end
+
+  def readme_cache_key
+    [@project.id, @project.commit.sha, "readme"].join('-')
+  end
 end

app/views/projects/show.html.haml

@@ -49,7 +49,8 @@
             %i.fa.fa-file
             = readme.name
       .wiki
-        = render_readme(readme)
+        = cache(readme_cache_key) do
+          = render_readme(readme)
   - else
     %h3.page-title
       This project does not have README yet