Added Copy of the “Purloined Proof”

In “The Purloined Proof” I told the story of…well, a purloined proof.  I did not include the actual proof, though.  I have now added it, though I have not said who did the “purloining”.  The interested reader may be able to find out for themselves.  Certainly, mathematicians should be able to if they want to spend the time doing so.