Abstract kbucket unit tests from GUID implementation.
[TDD] Unit tests for node/connection.py.

* Check initialization of PeerConnection and CryptoPeerConnection.
CryptoPeerConnection provides own equality.
Be consistent with parent class.
Make unused variable private.

* Enable pylint to flag future usage outside of class.
Set nickname in the parent class.
The parent class sets the logger.
Install the logger last.
Remove unused argument from __init__.
Remove contact tests.
Remove unused contact.py.