Using inheritance for TimeDep classes
Using inheritance for TimeDep classes

The TimeDep2dRigid class is now a child of the TimeDep class which
prevents the reuse of code. The only difference in the methods for the
displacement is the use of rigid bodies vs individial particles which
isa handled by the unwrap function.

malramsay64/MD-Molecules-Hoomd,malramsay64/MD-Molecules-Hoomd