relax SVN archive

This changes the first line of the 'relax' file. The change was suggested by Douglas Kojetin
(douglas dot kojetin at gmail dot com) in the post located at
https://mail.gna.org/public/relax-devel/2006-11/msg00098.html (Message-id:
<0E180DBB-896A-45F6-B19D-D6A02FD2BA4A@...>).

The change allows relax to run on Mac OS X by just typing 'relax'. This is because the python
binary is located at '/sw/bin/python'.