JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap-theme.min.css">
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.4.0/css/font-awesome.min.css">
<div class="col-xs-3 col-sm-3">
  <button type="button" class="btn btn-default btn-md btn-block"><i class="fa fa-plus"></i> Add New Item</button>
</div>

CSS

@media only screen and (max-width: 767px) {
    button {
        content: '<i class="fa fa-plus"></i>';
    }
}