Update Mustache render function (.to_html deprecated now).

[alexis-renard]

This was not functional with the current version of mustache. Please update the README or adapt the code accordingly. :)

[mhw]

See also https://github.com/mhw/jquery-Mustache which builds on Alexis' fix. I've reconciled a divergence between jquery.mustache.js and src/jquery.mustache.js and rebuilt the concatenated file.