nearly incompressible neo-hookean not working...
after all 1/2 has been creating 0...
before merging to poro
before merging to poro
now have many different formulations of compressible and nearly incompressible neo-hookean

Merge branch 'poro' into poro-old

Conflicts:
	vic-main.py
confirmed that PK1 -> PK2 stresses derivation working