Run on Mac OSX

Fixes to get it running for me on Mac OSX (10.6 Snow Leopard)

 * find GNU sed  (default is crappy BSD-ish sed)
 * "echo -n" seems to print the "-n".  Confusing, since /bin/sh is bash.  I just removed it anyways.

OK, i posted this with the github's in-browser editor but it seems to have screwed up a bunch of the control characters.  The only actual changes to use are near the top for those two things there.