Update the index page to announce 1.3.1.
Update the index page to announce 1.3.1.

* www/index.html: Latest version is 1.3.1.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion