feature: python3, secret chat

[exander77]

Moved to python3, secret chat, command line.

usage: teletun.py [-h] [-r] [-e] [-p SRC] [-s DST] [-m MASK] [-n MTU]
                  [-H HOST] [-P PORT] [-a]
                  peer_id

Teletun - IP over Telegram

positional arguments:
  peer_id               peer id (list for contact list)

optional arguments:
  -h, --help            show this help message and exit
  -r, --server          server
  -e, --encrypted       secret chat
  -p SRC, --src SRC     peer address
  -s DST, --dst DST     server address
  -m MASK, --mask MASK  mask
  -n MTU, --mtu MTU     MTU
  -H HOST, --host HOST  Telegram host address
  -P PORT, --port PORT  Telegram port
  -a, --auto            autoconfig from server

[PiMaker]

I am continuously amazed how people still find and regularly star this repository 3 years after I made it as a joke... And then you come along and create this pull request.

You're either very determined, or very bored 😄 Either way, thank you!