Version 0.4.0

Added

• Support for granting additional capabilities to containers. @mateuszlewko
• Support for all new options of resolv_conf added in Systemd 246. @mateuszlewko
• Ensure images can be safely downloaded in paralell.
• Ported tests from exec driver to this project. They cover basic
  functionality like starting, stopping, killing, destroying tasks and
  executing commands in them.
• Added Makefile for common build operations.

Changed

• Improved error message if systemd-nspawn fails to start a task.
• NewNspawnDriver() now returns a driver with the default config settings.

Fixed

• Fixed a runtime panic which occured if a task had no resources assigned.