release 4.40

• added python 3.5 to supported versions and configs
• support for metadata added to the name server (list of strings per registration).
  This provides a service like yellow-pages where you can query on category (for instance).
  You need to use memory or sqlite storage for this; the dbm storage doesn't support it.
• name server also has a new method set_metadata(), to set new metadata for an existing registration
• nsc tool has new commands to deal with metadata in the name server: setmeta, listmeta_all and listmeta_any
• removed obsolete stdinstdout example, it depended on exposing private attributes and Pyro hasn't allowed this anymore for quite some time (4.27)
• removed a problematic ipv6 unittest, and an often-failing workaround to determine the ipv6 address
• added current_context.client_sock_addr containing the address of the client doing the call
• current_context is now correct for oneway calls and async calls
• fixed some copy methods to correctly deal with possible subclassing (Proxy)