Timed comments on the waveform

Each comment sits as a dot under the moment it was left at. When the music
gets there the dot pings and a bubble grows out of it on a spark, then drifts
up and fades; a mouse over a dot peeks at it. The server fetches the newest
60 comments from pl8list on demand and keeps them for 15 minutes. A setting
turns them off.

web/index.html

@@ -144,6 +144,7 @@
       <label><input type="radio" name="crossfade" value="8"> dj mix</label>
     </fieldset>
     <label class="switch"><input type="checkbox" name="bass"> <span>bass boost</span></label>
+    <label class="switch"><input type="checkbox" name="comments"> <span>comments on the waveform</span></label>
     <fieldset class="modes">
       <legend>sleep timer <span id="sleep-left"></span></legend>
       <label><input type="radio" name="sleep" value="off"> off</label>