Allow markdown tables

lib/gitlab/markdown.rb

@@ -63,7 +63,7 @@ module Gitlab
         insert_piece($1)
       end
-      sanitize text.html_safe, attributes: ActionView::Base.sanitized_allowed_attributes + %w(id class)
+      sanitize text.html_safe, attributes: ActionView::Base.sanitized_allowed_attributes + %w(id class), tags: ActionView::Base.sanitized_allowed_tags + %w(table tr td th)
     end
     private