Changes

• All clients now support IPv6 addresses for both DNS and IP entries in host list - [Feature] IPv6 support #291
• Added ipv6_only flag to ParallelSSHClient and SSHClient for choosing only IPv6 addresses when both v4 and
  v6 are available.
• Removed Python 2 from binary wheel compatibility as it is no longer supported and not guaranteed to work.
• Host name is now an argument for all exceptions raised by single clients.

Fixes

• HostOutput would have empty host on some exceptions when stop_on_errors is False - HostOutput has empty host when authentication fails #297
• Race condition when forcefully closing channel via SSHClient.close_channel while channel data was left unread.