Added instructions for prototype version testing.

----- Instructions ----- 
Download .zip file, and extruct it.
Run prototype.exe
Internet connection required! (Its server based multiplayer)

----- Controls ----- 
WASD - for driving
Space - for handbrake
For fill gas or fixing car press F
Gamepad/Xbox controllers not implemented yet.

PS. I didn't made exit button yet :D So press Alf+f4 to exit game :D