Change __getitem__ to get the latest value from a parser
Change __getitem__ to get the latest value from a parser

This change is a generalization of what the method did before.
Now, instead of just looking at the last parser set, we look at
all of them starting from the last one.

crcollins/chemtools-webapp,crcollins/chemtools-webapp,crcollins/chemtools-webapp,crcollins/chemtools-webapp,crcollins/chemtools-webapp