Get some real-world looking worlds

[irapha]

Potentially some from https://github.com/austin-robot/utexas-art-ros-pkg/tree/master/stacks/art_vehicle/simulator_art

[irapha]

First three worlds being worked on are simple:

• simple road
• road with obstacle the car can swerve around
• road with obstacle the car can't swerve around and has to stop