make heatmap insensitive to dom position

hypothesis/js/src/hypothesis.coffee

@@ -32,9 +32,9 @@ class Hypothesis extends Annotator
     # Set up interface elements
     this._setupHeatmap()._setupSidebar()
 
-    @heatmap.element.appendTo(@sidebar)
     @viewer.element.appendTo(@sidebar)
     @editor.element.appendTo(@sidebar)
+    @heatmap.element.appendTo(@sidebar)
     @sidebar.appendTo(@wrapper)
 
     @plugins.Auth.withToken (token) =>

hypothesis/sass/app.scss

@@ -118,6 +118,8 @@ $iconset: iconset_wireframe;
   @include tinyshadow(-1px, 0, 0.2);
   background: hsla(0, 0, 90%, 0.4);
   position: fixed;
+  top: 0;
+  margin-left: -$heatmap-width;
   width: $heatmap-width;
   z-index: 1;
 }