Python-based CCSD Amplitudes

[dgasmith]

Psi4 added the ability to pull CCSD amplitudes directly from the Python layer:

Ne = psi4.geometry("""
 0 1
 Ne 0.0 0.0 0.0
 symmetry c1
 """)
psi4.set_options({'basis': 'cc-pvdz', 'freeze_core': 'false'})

_, wfn = psi4.energy('ccsd', return_wfn=True, molecule=Ne)
amps = wfn.get_amplitudes()

TIjAb = amps['tIjAb'].to_array()
TIA = amps['tIA'].to_array()

Full PR here. #39 reminded me of this and may simplify the T2 acquisition procedure greatly.