Tweeper depends on php-symfony-serializer which is used to convert json to xml
for some sites which provide the timeline data in json rather than in usable
html.
+
+NOTE: Tweeper also depends indirectly on php-symfony-property-access because
+the code relies on the ObjectNormalizer class which requires the
+PropertyAccess component, see
+http://symfony.com/doc/current/components/serializer.html#installation