Implemented randomization and tested in main

Ran into problems with using ballArray[1] as an independent variable.
Seems to be actually a display object, and therefore these objects do
not have their own attributes like "speedX or speedY". Left changes
uncommented. Will comment and make work for next commit.
Reset "setLinearVelocity" values for functionality

ISSUE: Position and speed are not being randomly generated, although the
Ball class is using math.random() to create them. Might be something to
do with how our "objects" are generated in main.lua.