Add velocities and angular momenta to Superstars
Make various parameters modifiable
Add function to calculate cluster energy
Add self-force term to force calculation
Split sqr() into a Utils.hpp file
Add Stepper abstract base class
Add Free and Interaction Steppers
Add Leapfrog Stepper
Add ReadCluster function
Add ModifiedEulerStepper
Add WriteCluster function
Add executable for testing energy conservation
Add EvolveCluster executable
Allow choosing stepper at runtime
Add executable to make a random cluster, use c++11

This uses the C++11 random number generator classes.
Allow dumping cluster state at several times