Move the note popups up slightly

The default position makes it hard to grab the marker and move it
when adding a note, so move themm up a few pixels.

app/assets/javascripts/index/notes.js.erb

@@ -110,6 +110,7 @@ $(document).ready(function () {
       minWidth: 320,
       maxWidth: mapSize.y * 1 / 3, 
       maxHeight: mapSize.y * 2 / 3, 
+      offset: new L.Point(0, -3),
       autoPanPadding: new L.Point(60, 40)
     };
   }