You can actually do it with label, you just have to hide the input.
<!-- head -->
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css" rel="stylesheet"/>
<!-- body -->
<label for="upload">
<span class="glyphicon glyphicon-folder-open" aria-hidden="true"></span>
<input type="file" id="upload" style="display:none">
</label>