<html>
  <head>
    <title>AbaPlan Project</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <base href="/">
    <!-- index.html -->
    <!-- <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"> -->
    <link href="node_modules/bootstrap/dist/css/bootstrap.min.css" rel="stylesheet">

    <!-- Third party libraries -->
    <!-- load Esri library -->
    <!--<script src="//js.arcgis.com/3.18/"></script>
    <link rel="stylesheet" href="//js.arcgis.com/3.18/esri/css/esri.css">-->
    <script src="https://js.arcgis.com/3.18/" data-dojo-config="async: true"></script>
    <!-- This is loaded in touchpad module -->
    <!--<script src="https://maps.googleapis.com/maps/api/js" data-dojo-config="async: true"></script>-->

    <link rel="stylesheet" href="//js.arcgis.com/3.18/esri/css/esri.css">
    <script>
        require(["/dist/vendor.bundle.js", "/dist/main.bundle.js"], function (vendor, main) {});
    </script>
  </head>

  <!-- 3. Display the application -->
  <body>

    <aba-plan>Loading...</aba-plan>

  </body>
</html>

<html>
  <head>
    <title>AbaPlan Project</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <base href="/">
    <!-- index.html -->
    <!-- <link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"> -->
    <link href="node_modules/bootstrap/dist/css/bootstrap.min.css" rel="stylesheet">

    <!-- Third party libraries -->
    <!-- load Esri library -->
    <!--<script src="//js.arcgis.com/3.18/"></script>
    <link rel="stylesheet" href="//js.arcgis.com/3.18/esri/css/esri.css">-->
    <script src="https://js.arcgis.com/3.20/" data-dojo-config="async: true"></script>
    <!-- This is loaded in touchpad module -->
    <!--<script src="https://maps.googleapis.com/maps/api/js" data-dojo-config="async: true"></script>-->

    <link rel="stylesheet" href="//js.arcgis.com/3.20/esri/css/esri.css">
    <script>
        require(["/dist/vendor.bundle.js", "/dist/main.bundle.js"], function (vendor, main) {});
    </script>
  </head>

  <!-- 3. Display the application -->
  <body>

    <aba-plan>Loading...</aba-plan>

  </body>
</html>

Change to Esri 3.20 instead of 3.18
Change to Esri 3.20 instead of 3.18
