O.V.P. acknowledges funding from the U.S. Department of Energy, Grant DE-SC0014429, and is grateful to the Donostia International Physics Center for support during a summer visit. W.L. acknowledges startup funding by Hunan Agricultural University, Grant 540499818006. J.T. acknowledges support by the National Nature Science Foundation of China, Grant 51301066. D.C. acknowledges support from the Basque Government (Project IT588-13) and IKERBASQUE, Basque Foundation for Science. The simulations were performed at the University of Southern California’s Center for High-Performance Computing (hpcc.usc.edu).