OpenBazaar/OpenBazaar — pull request #723 by Renelvon (2014-10-02 13:15:10+00:00)
Title: Refactor code in connection.py

### Motivation
Refactor code in `node/connection.py` so that it is easier to read and test.

### Changelog
* Rewrite methods to bring failure cases in front and avoid multiple nested `if` and `try` statements.
* Optimization: Delay data compression in `PeerConnection.send_raw` until we are sure we'll send them.
* Strip `try-except` from `PeerConnection.create_zmq_socket`; caller already handles exceptions.
* Refactor and DRY `CryptoPeerConnection.check_port`.
* Prefer ipv6 over ipv4 sockets.
* Create sockets inside `with` to ensure they are closed upon termination.
* Some other minor style changes.