Version 1.8.1

Release 1.8.1 (2016-10-24)

• Sessions have a new option save_accessed_time which defaults to true for
  backwards compatibility. Set to false to tell beaker not to update
  _accessed_time if the session hasn't been changed, for non-cookie sessions
  stores. This lets you avoid needless datastore writes. _accessed_time will
  always be updated when the session is intentionally saved.
• data_serializer parameter in Session accepts a custom object with dumps and loads methods.
• Fixed a TypeError in exception reporting when failing to load a NamespaceManager
• Allow to change Cookie Expiration from a value back to None, previously it had no effect.
• Allow SessionMiddleware to setup a custom Session class through the session_class argument.
• Added invalidate_corrupt option to CookieSessions too for valid cookies containing invalid data.