Vertikālā izlīdzināšana centrā programmā Bootstrap 4

var currentAuthor = "";
var currentQuote  = "";
function randomQuote() {
  $.ajax({
      url: "https://api.forismatic.com/api/1.0/?",
      dataType: "jsonp",
      data: "method=getQuote&format=jsonp&lang=en&jsonp=?",
      success: function( response ) {
        $("#quote-content").html('<h2 id="quote-content" class="display-5"><i class="fa fa-quote-left" aria-hidden="true"> ' + response.quoteText + ' <i class="fa fa-quote-right" aria-hidden="true"></i></h2>');
        $("#quote-author").html('<p id="quote-author" class="lead"><em>' + response.quoteAuthor + '</em></p>');

        currentAuthor = response.quoteAuthor;
        currentQuote  = response.quoteText
      }
  });
}

function openURL(url){
  window.open(url,'Share', 'width=550, height=400, toolbar=0, scrollbars=1 ,location=0 ,statusbar=0,menubar=0, resizable=0');
}

function tweetQuote(){
      openURL('https://twitter.com/intent/tweet?hashtags=quotes,freecodecamp&related=freecodecamp&text=' + encodeURIComponent('"' + currentQuote + '" - ' + currentAuthor));
}

$(document).ready(function () {
    randomQuote();

    $("#get-another-quote-button").click(function(){
        randomQuote();
    });

   $('#tweet').on('click', function() {
       tweetQuote();
   });
});

html, body {
  background-image: url("https://www.mylinea.com/wp-content/uploads/beautiful-trees-stock-photo-055.jpg");
    background-color: #17234E;
    margin-bottom: 0;
    min-height: 30%;
    background-repeat: no-repeat;
    background-position: center;
    -webkit-background-size: cover;
    background-size: cover;
}

.btn-new-quote {
    color: #0C0C0D;
    background-color: transparent;
    border-color: #414147;
}

.btn-new-quote:hover {
    color: #0C0C0D;
    background-color: #9A989E;
    border-color: #0C0C0D;
}

#tweet {
    color: RGB(100, 100, 100);
}

#tweet:hover {
    color: RGB(50, 50, 50);
}

.jumbotron {
    position: relative;
    top: 50%;
    transform: translateY(-50%);
    opacity: .85;
    border-color:  RGB(50, 50, 50);
    padding-bottom: 8px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0-alpha.6/css/bootstrap.min.css">
<div class="container">
    <div class="row justify-content-center align-self-center">
        <div class="col-sm-6">
            <div class="jumbotron vertical-center text-center">
                <h2 id="quote-content" class="display-5"><i class="fa fa-quote-left" aria-hidden="true"></i><i class="fa fa-quote-right" aria-hidden="true"></i></h2>
                <p id="quote-author" class="lead"><em></em></p>
                <hr class="my-2">
                <div class="row align-items-center justify-content-between">
                    <div class="col-sm-1-4 text-left">
                        <a id="tweet" href="#">
                            <h2 class="display-4"><i class="fa fa-twitter" aria-hidden="true"></i></h2>
                        </a>
                    </div>
                    <div class="col-sm-1-4 text-right">
                        <button id="get-another-quote-button" type="button" class="btn btn-outline-secondary  btn-new-quote">Don't Quote Me on This...</button>
                    </div>

                </div>
            </div>
        </div>
    </div>
</div>