message: Add tabs and improve quality layers
diff: <script type="text/javascript" src="lib/highcharts.js"></script>
  <script type="text/javascript" src="erizo.js"></script>
  <script type="text/javascript" src="quality_layers.js"></script>
  + <style>
  + /* Style the tab */
  + div.tab {
  + overflow: hidden;
  + border: 1px solid #ccc;
  + background-color: #f1f1f1;
  + }
  +
  + /* Style the buttons inside the tab */
  + div.tab button {
  + background-color: inherit;
  + float: left;
  + border: none;
  + outline: none;
  + cursor: pointer;
  + padding: 14px 16px;
  + transition: 0.3s;
  + font-size: 17px;
  + }
  +
  + /* Change background color of buttons on hover */
  + div.tab button:hover {
  + background-color: #ddd;
  + }
  +
  + /* Create an active/current tablink class */
  + div.tab button.active {
  + background-color: #ccc;
  + }
  +
  + /* Style the tab content */
  + .tabcontent {
  + display: none;
  + padding: 6px 12px;
  + border: 1px solid #ccc;
  + border-top: none;
  + }
  +</style>
  </head>
  <body>
  + <div id="tabs" class="tab"></div>
  + <div id="charts"></div>
  </body>
  </html>
  