The SDF files for charged compounds aren't listing the formal charges of the atoms

[guoweiqi]

example, butylammonium: https://github.com/MobleyLab/benchmarksets/blob/master/input_files/cd-set1/sdf/guest-1.sdf

[davidlmobley]

Interested in putting in a PR to fix?

[guoweiqi]

Attempted fix here:

#69