Ignore case completely in fields parameter

[sckott]

Is there any reason to care about case at all? e.g., why not let SpecCode, Speccode, and speccode all work? Will see if there's any tables with fields with the same name but different cases

[sckott]

from ropensci/rfishbase#90

[cboettig]

good question, I don't think there's any situation where case matters, so that's probably a good fix

[sckott]

cool, will make sure it won't break anything first