Add pagination to labels page

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

app/views/projects/labels/index.html.haml

@@ -10,6 +10,7 @@
 - if @labels.present?
   %ul.bordered-list.manage-labels-list
     = render @labels
+  = paginate @labels, theme: 'gitlab'
 
 - else
   .light-well