Improvements to the simulation characteristics of "Car Project"

Eddie,

I enjoyed looking at the Car Project code. Great job using Javadoc, and including a test for the Car class. I hope you don't mind me making a couple of improvements!

In this pull request, you should see a list of commits. If you click on each of the commits, individually, you can see what code was changed for just that commit.

With the exception of b98823a, b7a3636, 8a3d282, and 21f1b50, you should review each commit thoroughly before merging and confirming.

This pull request issue is a good place to leave comments, too.