Undesired side effect of "Drop all caps" flag

[gutierrezps]

First of all, nice project!

I have found an issue while tidying my BibTeX file. When checking the "Drop all caps" flag, publisher/institute/school tags composed only by acronyms (e.g. IEEE, UFRJ) became capitalized (e.g. Ieee, Ufrj). I'm not sure how you could deal with this, perhaps adding an option to exclude those tags?

[ianhellstrom]

Possibly the same request as
#49