Update CHANGES (releng for 2.4)

CHANGES

@@ -1,3 +1,21 @@
+2016-11-20 VERSION 2.4
+ * Fix compatibility with nginx-1.7.12+.
+ * explain the purge logic
+ * feat(purge all): Include option to purge all the cached files
+ This option can be slow if a lot of content is cached, or if the
+ storage used for the cache is slow. But you really should be using
+ RAM as your cache storage.
+ * feat(partial keys): Support partial keys to purge multiple keys.
+ Put an '*' at the end of your purge cache URL.
+ e.g:
+ proxy_cache_key $scheme$host$uri$is_args$args$cookie_JSESSIONID;
+ curl -X PURGE https://example.com/pass*
+ This will remove every cached page whose key cache starting with:
+ httpsexample.com/pass*
+ Be careful not passing any value for the values after the $uri, or put
+ it at the end of your cache key.
+ * Convert a config file to build a dynamic module
+
 2014-12-23 VERSION 2.3
  * Fix compatibility with nginx-1.7.9+.