A few updates to make the code more in-line with ROS 2 guidelines.

[pgold]

• CreateDriver derives from rclcpp::Node.
• Node::now is used instead of rclcpp::Clock::now.
• Use generic rclcpp::spin instead of CreateDriver having it's own spin loop.

[pgold]

Thanks for reviewing.

Sure thing! I was just waiting for the other PRs to be merged so that I can rebase and test this one.

[pgold]

Rebased and tested.

[jacobperron]

@pgold If you'd like, feel free to open a PR adding yourself to the "Contributors" list in the README: https://github.com/AutonomyLab/create_robot/tree/foxy#contributors

Thanks for the porting effort!