Atomic Unit Standardization of PyVibDMC

Previously, PyVibDMC file output was in atomic units, but any analysis or reading of that data was done in angstroms or cm-1. Now, the output has remained in atomic units, and the analysis code is by default still in atomic units. One can pass in an optional keyword argument in order to convert the output to angstroms/cm-1.

NOTE: This is not a backwards compatible change. Please be careful of loading in old data or using old code, now the default is atomic units for everything.

Full Changelog: 1.2.3...1.3.0