Change heading on trackerslist for a better HTML outline

Blockdown.coffee

@@ -683,7 +683,7 @@ class Blockdown
 			trackersListCode = ''
 			if @rendering == @site
 				# Site code
-				trackersListCode = "<aside id='trackers-list' class='mfp-hide'>\n\t<h3>#{numberOfTrackers} trackers</h3>\n\t<ul>#{trackersList}\t\t</ul>"
+				trackersListCode = "<aside id='trackers-list' class='mfp-hide'>\n\t<h4>#{numberOfTrackers} trackers</h4>\n\t<ul>#{trackersList}\t\t</ul>"
 			else
 				# App code
 				trackersListCode = "<script>var trackersList = #{JSON.stringify trackersArray};</script>"