Update changelog ahead of patch release

CHANGELOG.rst

@@ -7,6 +7,14 @@
 Changelog
 ---------
 
+v2.2.4 2015-12-17
+=================
+
+Bug fixes:
+ * Fix Markdown rendering issue
+ * Return default error page on fanstatic errors
+ * Prevent authentication when using API callbacks
+
 v2.2.3 2015-07-22
 =================
 
@@ -239,6 +247,14 @@ Troubleshooting:
    leaving the fields empty. Also make sure to restart running processes like
    harvesters after the update to make sure they use the new code base.
 
+v2.1.6 2015-12-17
+=================
+
+Bug fixes:
+ * Fix Markdown rendering issue
+ * Return default error page on fanstatic errors
+ * Prevent authentication when using API callbacks
+
 v2.1.5 2015-07-22
 =================
 
@@ -406,6 +422,14 @@ Known issues:
  * Under certain authorization setups the frontend for the groups functionality
    may not work as expected (See #1176 #1175).
 
+v2.0.8 2015-12-17
+=================
+
+Bug fixes:
+ * Fix Markdown rendering issue
+ * Return default error page on fanstatic errors
+ * Prevent authentication when using API callbacks
+
 v2.0.7 2015-07-22
 =================