Fixes flickering when mouse moves between nodes labels

w/ a secret rect!

client/app/scripts/charts/node.js

@@ -92,6 +92,12 @@ export default class Node extends React.Component {
     return (
       <g className={className} transform={transform} onClick={this.handleMouseClick}
         onMouseEnter={this.handleMouseEnter} onMouseLeave={this.handleMouseLeave}>
+        <rect className="hover-box"
+          x={-nodeScale(scaleFactor * 0.5)}
+          y={-nodeScale(scaleFactor * 0.5)}
+          width={nodeScale(scaleFactor)}
+          height={nodeScale(scaleFactor) + subLabelOffsetY}
+          />
         <text className="node-label" textAnchor="middle" style={{fontSize: labelFontSize}}
           x="0" y={labelOffsetY + nodeScale(0.5 * scaleFactor)}>
           {labelText}

client/app/styles/main.less

@@ -338,6 +338,10 @@ h2 {
     cursor: pointer;
     transition: opacity .5s @base-ease;
 
+    .hover-box {
+      fill-opacity: 0;
+    }
+
     &.hovered text {
       stroke: @background-average-color;
       stroke-width: 8px;