Clean up the units

[apizzuto]

"erg/year? Yuck! this includes providing more clear units for the case of transient simulation."

[renereimann]

Using erg/year or erg/s is the standard in astrophysics community. You can see that the Waxman and Murase paper (https://arxiv.org/abs/1607.01601) or Mertsch et al (http://arxiv.org/abs/1612.07311) all use these units.