[plt-scheme] starting to write another set of incomplete notes: (lib "class.ss")

Hi everyone,

I've written some more notes that might be useful for newcomers like
myself coming from "mainstream" languages:

    http://hkn.eecs.berkeley.edu/~dyoo/plt/oop-notes.text

It's still very rough, but I thought I might as well link it and get some
feedback as I start fleshing it out more.  Hope this helps!