ROS update

I have created and uploaded a virtual machine that can be used VirtualBox. Hopefully this can be used on Mac systems as well. Please try this and come back to me with feedback. The virtual machine download link can be found here

https://github.uio.no/TEK4030/tek4030_ros_intro/blob/master/README.md#using-a-premade-ros-virtual-machine

Some of you had trouble with compiling planar_robot_simulator yesterday. I have downloaded and compiled this package on my own system and the virtual machine, and there were no problems. The fault might be something wrong in the configuration of CMakeLists.txt. If you can't find a solution, please send me an e-mail with the code attached, and I will look into this.