title: vuetify parallax fluid template issue
body: <p>I am trying to setup a fluid template to be used in responsive design viewports. 
  On medium viewports ( md ) the display is fine . ... see <a href="https://codepen.io/erwin16/pen/QxmrvK" rel="nofollow noreferrer">codepen</a>
  the 3 v-card ( rounded) are in a row... ( parallax background image height is 380px)</p>
  
  <p>however it does not scale right on smaller viewports ( sm or xs )
  all v-catds are not displayed, because the height of the parallax background image is not adjusted ( it's still 380px height)</p>
  
  <p>how can I set it up right , in order to get in smaller viewports all my v-cards in column</p>
  
  <p><strong>HTML</strong></p>
  
  <pre><code>    &lt;div id="app"&gt;
        &lt;v-app id="inspire"&gt;
          &lt;v-parallax src="https://vuetifyjs.com/static/doc-images/parallax/material2.jpg" height="380"&gt;
            &lt;v-layout row wrap align-center justify-center&gt;
              &lt;v-flex xs12 sm12 md3&gt;
                  &lt;v-card class="elevation-0 rounded-card"&gt;
                    &lt;v-card-title primary-title class="layout justify-center"&gt;
                      &lt;h1&gt;TITLE 1&lt;/h1&gt;
                      &lt;/v-card-title&gt;
                    &lt;v-card-text&gt;
                      ipsum dolor sit amet, consectetur adipiscing elit. Quisque cursus enim et justo eleifend pharetra. Nam consectetur, nulla in viverra mattis, ipsum libero faucibus odio, at eleifend mauris arcu non nibh. Aliquam congue augue sed sapien tristique, eget faucibus risus pulvinar. Nullam ut nunc felis.
                    &lt;/v-card-text&gt;
                  &lt;/v-card&gt;
               &lt;/v-flex&gt;
               &lt;v-flex xs12 sm12 md3 offset-md1&gt;
                  &lt;v-card class="elevation-0 rounded-card"&gt;
                    &lt;v-card-title primary-title class="layout justify-center"&gt;
                      &lt;h1&gt;TITLE 2&lt;/h1&gt;
                      &lt;/v-card-title&gt;
                    &lt;v-card-text&gt;Proin felis diam, placerat ut lacinia viverra, dapibus ut sapien. Curabitur non dolor sed tortor aliquet lacinia. Maecenas ut porta velit, vel elementum sem. Quisque tincidunt vel nisl quis dignissim. Suspendisse accumsan leo sed neque sodales, in congue metus egestas. Maecenas molestie, eros.
                    &lt;/v-card-text&gt;
                  &lt;/v-card&gt;
               &lt;/v-flex&gt;
                       &lt;v-flex xs12 sm12 md3 offset-md1&gt;
                  &lt;v-card class="elevation-0 rounded-card"&gt;
                    &lt;v-card-title primary-title class="layout justify-center"&gt;
                      &lt;h1&gt;TITLE 3&lt;/h1&gt;
                      &lt;/v-card-title&gt;
                    &lt;v-card-text&gt;
                      Quisque non felis massa. Suspendisse vel aliquam orci, eget aliquet est. In efficitur nisi vel massa volutpat, vitae varius velit volutpat. Duis non maximus nunc, ut tincidunt eros. Aliquam erat volutpat. Vestibulum libero justo, euismod et massa finibus, tincidunt euismod libero.
                    &lt;/v-card-text&gt;
                  &lt;/v-card&gt;
               &lt;/v-flex&gt;
            &lt;/v-layout&gt;
          &lt;/v-parallax&gt;
        &lt;/v-app&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p><strong>CSS</strong></p>
  
  <pre><code>    .rounded-card {
        border-radius: 50px;
      }
      .card__text {
        font-size: 1.2em;
        padding-top: 0;
        padding-bottom: 3em;
      }
  </code></pre>
  
  <p><strong>JS</strong></p>
  
  <pre><code>    new Vue({
        el: '#app',
  
      })
  </code></pre>