Pin pytz<=2014.2 to fix unit tests for time being (no pun intended)

fixes #184
Added ability to specify remote port for NetDevice objects

fixes #172

+ Bugfix when passwords are passed in to make sure they are not unicode
+ Add defaults in settings.py for SSH (SSH_PORT) and Telnet (SSH_TELNET) ports
+ Added documentation for SSH_PORT and TELNET_PORT in settings.py