Improve parseJSON failure message for Either
Improve parseJSON failure message for Either

This fixes #193.

JPMoresmau/aeson,nurpax/aeson,dmjio/aeson,plaprade/aeson,SeanRBurton/aeson,sol/aeson,neobrain/aeson,23Skidoo/aeson,aelve/json-x,beni55/aeson,jkarni/aeson,bwo/aeson,sol/aeson,neobrain/aeson,abbradar/aeson,roelvandijk/aeson,roelvandijk/aeson,lykahb/aeson,timmytofu/aeson,sol/aeson