Improve copy to clipboard button

See http://getbootstrap.com/docs/4.0/components/input-group/#button-addons

app/templates/users/profile.html

@@ -7,12 +7,12 @@
   {% if generated_token %}
   <div class="row">
       <div class="input-group">
-        <div class="input-group-addon">
-          <button id="copyToken" type="button" class="btn btn-primary" data-clipboard-target="#generatedToken"
+        <span class="input-group-btn">
+          <button id="copyToken" type="button" class="btn btn-secondary" data-clipboard-target="#generatedToken"
             data-toggle="tooltip" data-placement="bottom" title="Copied!">
             <span class="oi oi-clipboard" title="Copy to clipboard" aria-hidden="true"></span>
           </button>
-        </div>
+        </span>
         <input type="text" class="form-control" id="generatedToken" value="{{ generated_token }}" readonly>
       </div>
   </div>