Updates social-links.html

Adds lines 56-60: stackoverflow link

Author: rowmatrix

_includes/social-links.html

@@ -52,6 +52,13 @@
             <svg class="icon icon-github"><use xlink:href="#icon-github"></use></svg>
         </a>
     {% endif %}
+    
+    {% if site.stackoverflow %}
+        <a class="link" data-title="stackoverflow.com/users/{{ site.stackoverflow }}" href="http://stackoverflow.com/users/{{ site.stackoverflow }}" target="_blank">
+            <svg class="icon icon-stackoverflow"><use xlink:href="#icon-stackoverflow"></use></svg>
+        </a>
+    {% endif %}
+
 
     {% if site.medium %}
         <a class="link" data-title="medium.com/@{{ site.medium }}" href="https://medium.com/@{{ site.medium }}" target="_blank">