Bump to v2.3.1
Bump to v2.3.1

bobthecow/mustache.php,BrunoDeBarros/mustache.php,irontec/mustache,cgvarela/mustache.php,zuluf/mustache.php,thecocce/mustache.php,ericariyanto/mustache.php,evdevgit/mustache.php,sophatvathana/mustache.php