Add a rollover count so limits are obeyed

Limits in file size don't seem to obey unless set to > 1.
More sane logging level by default
Merge pull request #721 from hoffmabc/fix-logging-i

Fix logging issues
Refactor code in connection.py

* Refactor PeerConnection.create_zmq_socket. Allow it to raise an
  exception; we are catching it elsewhere.
* Refactor PeerConnection.send_raw.
  * Make failure cases stand out.
  * Do not compress until ready to send.
* Make failure cases stand out in CryptoPeerConnection.start_handshake.
* Refactor and DRY CryptoPeerConnection.check_port.
  * Prefer ipv6 over ipv4 sockets.
  * Create sockets inside `with` to ensure they are closed upon termination.
* Shorten CryptoPeerConnection.sign.
* Straighten CryptoPeerConnection.encrypt.
* Refactor CryptoPeerConnection.send.
  * Make failure cases stand out.
  * Guard against encrypt returning False.
* Straighten PeerListener.listen.