This library was inspired by and derived from "johnboiles" (it seems) 
PCInt Arduino Playground example here: http://www.arduino.cc/playground/Main/PcInt
If you are the original author, please let us know at the google code page

It provides an extension to the interrupt support for arduino by
adding pin change interrupts, giving a way for users to have
interrupts drive off of any pin.

Please make any configuration changes in the accompanying PinChangeIntConfig.h file.
This will help avoid having to reset your config in the event of changes to the 
library code (just don't replace that file when you update).