Vibrational Averaging

[herbertludowieg]

Merging in the VA branch that was created to add a numerical calculation module, vibrational averaging. Additions:

• Zero-point Vibrational corrections of a specified property
• Vibrational Raman Optical Activity
• Expanded Gaussian and NWChem parsers
• Added relevant tests
• Added a lot of options to NWChem input generator

New additions in Gaussian output parser:

• Expanded frequency parsing to handle the HPModes keyword and ability to handle parsing the frequencies from a geometry optimization and frequency calculation
• Added gradient parser
• Added NMR shielding tensor parser
• Fixed orbital parsing to grab the last population analysis from a geometry optimization
• Added parser to grab the extended properties from a frequency calculation such as IR intensities and reduced masses

New additions in Gaussian Fchk parser:

• Added frequency parser
• Added parser to grab extended properties from frequency calculation
• Added NMR shileding tensor parser (this grabs the tensors in Hz I believe needs some unit analysis)
• Added gradient parser

New additions in NWChem output parser:

• Added raman optical activity parser
• Added gradient parser

[avmarchenko]

I was able to get checks to pass locally on python 3.5 and 3.6. I think it is safe to merge. We should open an issue to look into the travis/appveyor configuration.