Update to README, and resource leak fix

The README was pointing people to an older version of slamhound, that still had a problem with truncating large files.

Also, I believe that there was a file leak going on in swap-in-reconstructed-ns-form where the PushBackReader created was never closed.  This tends to work fine with a deleteOnExit file   under Linux, but I know from experience that it will cause the file not to be deleted under Windows.