added a memcached option. It's really slow though. don't use it.

overviewer.py

@@ -350,6 +350,8 @@ dir but you forgot to put quotes around the directory, since it contains spaces.
     # Set up the cache objects to use
     caches = []
     caches.append(cache.LRUCache(size=100))
+    if config.get("memcached_host", False):
+        caches.append(cache.Memcached(config['memcached_host']))
     # TODO: optionally more caching layers here
 
     renders = config['renders']