Log Message:
Update net/py-netlib to py-netlib-0.13.1.

Changes:
0.13.1:
 o Misc bug fixes

0.13:
 o Misc bug fixes

0.12.2:
 o Add support for upstream certificate validation when using SSL/TLS with an
   instance of TCPClient
 o Remove certffi
 o Various HTTP/2 support improvements

0.12.1:
 o Implement basic HTTP/2 frame classes
 o Add ALPN support to TCP abstraction

0.12:
 o Bump dummy cert expiry to 5 years.
 o Add support for web sockets