I have been working also using the same site (openenergymonitor.org), and i made my calcualtions based on another pagehttp://openenergymonitor.org/emon/buildingblocks/ct-sensors-interface
This is a more simple project to just get the current calculations from the CT sensor.
I believe my calculations for the voltage divider should be correct.
Let me know when you start working on the library, i will be interested to help where i can.