Using new collisions

Collisions are based on intersections between wall rects and car rects.
The collisions on corners seem more realistic and there are less known
points to traverse walls. The downside is that on the right hand side of
walls there are issues but these seem less of a problem than the old
issues.
Updated readme
Changed test mode track length

Attempt to soften problems with sprite track positions
Power ups stored on car as hash map

We need the power ups currently set on the car to be stored as a hash
map so that they all have their own time received as some will not
interfere with each other (e.g. TimeSlow and Boost)
Extra comment