Add @PythonSprints tweets to footer

Author: kynan

_includes/footer.html

@@ -6,7 +6,7 @@
                data-height="400"
                data-theme="light"
                data-link-color="#2B7BB9"
-               href="https://twitter.com/py_sprints?ref_src=twsrc%5Etfw">Tweets by py_sprints</a>
+               href="https://twitter.com/PythonSprints">Tweets by @PythonSprints</a>
             <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
         </div>
         <div class="col-md-7">