Add no-cache as a response header.

util/cache.py

@@ -10,3 +10,12 @@ def cache_control(max_age=55):
       return response
     return add_max_age
   return wrap
+
+
+def no_cache(f):
+  @wraps(f)
+  def add_no_cache(*args, **kwargs):
+    response = f(*args, **kwargs)
+    response.headers['Cache-Control'] = 'no-cache'
+    return response
+  return add_no_cache