Add rudimentary border and increase squares' size for better performance

[neslinesli93]

Add the logic for a very rudimentary (ugly) border.
Hoping for help from a design guy :P

[igorantun]

What would be the advantage of this compared to #123 ?

[neslinesli93]

My implementation draws a rectangle around the playground.
#123's implementation draws infinite lines on the border, which forms a rectangle but do not stop when they form a corner of such rectangle: they continue indefinitely.
So if you could zoom out, in my implementation you would see a black rectangle, in #123 's implementation you would see a '#' (a grid)

[keithagroves]

Also my implementation has collision detection but we can have both right? neslinesli93#1