Added a Global class for creating singleton objects,
namely SDL_Window and SDL_Renderer. Edited the makefile
to compile the Global class as well.`
Implemented prototype constructors for the Paddle class
to experiment with drawing paddles on the screen. Commented
out anything associated with the Point2d class. Not ready to
utilize that functionality yet.
Tried to use new Global class to instantiate the window in main, currently does not compile