title: ESLint warnings and error with vue.js - vue/require-default-prop & vue/require-prop-type-constructor
body: <p>I am creating my first SPA using Vue.js, Babel and WebPack. A Vue component has the following script:</p>
  
  <pre><code>&lt;script&gt;
  export default {
    props: {
      name: String,
      required: true
    }
  }
  &lt;/script&gt;
  </code></pre>
  
  <p>When I run eslint I get the following warnings and error:</p>
  
  <pre><code>8:5   warning  Prop 'name' requires default value to be set      vue/require-default-prop
  9:5   warning  Prop 'required' requires default value to be set  vue/require-default-prop
  9:15  error    The "required" property should be a constructor   vue/require-prop-type-constructor
  </code></pre>
  
  <p>I have copied the code from a tutorial I am following and I cannot understand how to fix it?</p>