renamed hubble_bodies to something cooler
Created script for testing spherical collapse model

Currently WIP
Increased framerate
added test for random_positions
explicitly test random_position for |R| < 1
fixed problem in random_positions with |R|<1
Made it work

works in comoving coordinates, then converts to physical
time varying scale factor included
currently built in assumption of critical density
various modifications to help explore hubble_bodies