added hoomd ethane xml
added hoomd ethane xml

Jonestj1/mbuild,summeraz/mbuild,sallai/mbuild,summeraz/mbuild,iModels/mbuild,ctk3b/mbuild,ctk3b/mbuild,tcmoore3/mbuild,Jonestj1/mbuild,sallai/mbuild,iModels/mbuild,tcmoore3/mbuild