C. Hayward, P. Torrey, V. Springel, L. Hernquist, and M. Vogelsberger. (2013)cite arxiv:1309.2942Comment: Submitted to MNRAS. Animations for all simulations available at http://www.cfa.harvard.edu/itc/research/arepomerger/ . 25 pages, 14 figures. Comments encouraged.