A few updates.
Getting closer to a working model.
Injection of gas particles now seems to work well enough.  The long term evolution is most effected by gradual inaccuracies due to the timestepping (the binary drifts and becomes more eccentric, even when accretion is set to add no mass or momentum).
Refactor of some of the binary accretion code.
Removed fixes for non-existant bug that was actual caused by mis-set mass in the initial conditions.
Pretty up indentation in hydra
Fixed form of softening potential
Updated initial conditions generator and correspondingly the inject_gas code too.
Merged binary into master.
Fix some rounding issues with z-components of velocity/position in 2D