Drawing function

I believe a more accurate way to track hands than the first attempt.
Now, you can increase/decrease size with left right arrow, pull "pen"
up/down with the up/down arrows, save the drawing with a click or just
clear the screen with ENTER. Also I made it so if you push TAB then it
will change the pen color to something random.
Merge branch 'Marwan' of https://github.com/liltove/SensoryPaint into Marwan