Bypass the rendering pipeline for highlighting to reduce (eliminate) latency

Fixes #15

Layout.js

@@ -227,7 +227,6 @@ class Layout {
           to: link.to,
           id: link.id,
           label: link.label,
-          highlight: link.highlight,
         });
       }
     }
@@ -240,7 +239,6 @@ class Layout {
     for (let link of links) {
       this.links_.push(
           new LayoutLink(link.from, link.to, link.id, link.label,
-                         link.highlight,
                          this.nodesByPos_, this.linksByPos_,
                          this.labelsByPos_));
     }