update README
fix overuse of the pronoun I

In the submission to CPS, one reviewer thought I used the word "I" too much and
that this thismakes the paper about the research and not the author. I've
thought carefully about this. It is important that I explain my views rather
than simply present them as my opinion, but I feelthat the use of the pronoun I
makes the writing a little clearer (and sometimes more accurate). In this
spirit, I've gone through and explained my statements a little more carefully.