<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>validation event example</title>
    <script src="../../node_modules/vue/dist/vue.js"></script>
    <script src="../../dist/vue-validator.js"></script>
    <style>
      input.invalid { border-color: red; }
      .errors { color: red; }
    </style>
  </head>
  <body>
    <div id="app">
      <label for="username">username:</label>
      <validity field="username" 
                ref="validity"
                v-model="validation"
      