market: reduce coupling between market and DHT implementation.

* Also decrease coupling by removing the return value,
  since it is not used anywhere.
transport: Refactor transport.store

* Turn it into a pure wrapper around dht.iterativeStore
  to reduce maintenance cost for changes in DHT.
an up to date changelog with the latest version number is necessary for the debian building tools. re-introducing changelog update lost on release-0.2.0 branch
fixes on ubuntu build folder that were breaking the build process.
Merge pull request #720 from Renelvon/decouple2

Decouple market implementation from DHT
Merge pull request #726 from gubatron/0.2.0-debian-builder-fixes

0.2.0 debian builder fixes
Refactor code in connection.py

* Drop unused PeerConnection.responses_received.
* Refactor PeerConnection.create_zmq_socket.
  * Allow it to raise an exception; we are catching it elsewhere.
  * Make it a private function.
* 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.
  * Remove hardcoded timeout. Use the instance attribute.
* Shorten CryptoPeerConnection.sign.
* Straighten CryptoPeerConnection.encrypt.
* Refactor CryptoPeerConnection.send.
  * Make failure cases stand out.
  * Guard against encrypt returning False.
* Remove PeerListener.cleanup_context. PeerListener no longer manages
  it own zmq.Context. Purge any references.
* Straighten PeerListener.listen.