Includes dynamical friction term (from Besla et al. 2007), Lambda = r/bmin, with bmin = 1.6*3 kpc.  Recovers position of LMC at -1 Gyr as per Besla et al. 2007.  sigma(r) from Zentner & Bullock 2003. Logical variables backward and forward to be set for doing backward or forward integration.  Note that integrating backward and integrating forward with the dynamical friction term now has satellites ending up at same place to better than 1 % accuracy.