More detailed output for saved array. Also write to npz file. Can specifiy index of saved array to go back to in the revert method.
Gravity is just set by the M_bh paramter.
_cons_update method--keeping track of changes of nominally conserved quantities as well as source terms.
Ipython notebooks are too annoyingto track.
Choice of whether or not to include gravitational velocity dispersion in the (effective) wind velocity.