Rotor counting inaccurate for certain species with triple bonds

[gmagoon]

RMG will incorrectly count rotors for certain species with triple bonds, which will affect the accuracy of Cp,Inf used in Wilhoit polynomial fitting. Examples include:

1. species where "internal" bond rotation corresponds to rotation of the entire molecule: e.g. CH3CCH (should be 0 rotors, but RMG will count the H3C-C rotor)
2. species with "degenerate" internal rotations: e.g. dimethylacetylene: CH3CCCH3 (should be 1 rotor, but RMG will count both H3C-C rotors)

Relevant section of code is ChemGraph's calculateInternalRotor().

[gmagoon]

A related potential issue involves resonant radicals like allyl (H2C=CH-CH2.). RMG will count one rotor, but one could make an argument for 0 or 2 rotors (depending on the temperature range of interest...I'm not sure of the barrier off the top of my head).