Added Cache-Controle: private header.

src/cache.py

@@ -155,6 +155,7 @@ class Cache:
         #try:
         web.http.modified(seconds_to_datetime(last_modified), self.etag())
         web.http.expires(timedelta(**self.expires))
+        web.header('Cache-Control', 'private')
 
         if not server_modified:
             # Concatenated content has not been loaded yet, read the cached