Description of Mustache library import into moodle.

Clone from https://github.com/moodle/custom-mustache.php

Rebase onto latest tag from https://github.com/bobthecow/mustache.php

Delete folder "test"

Delete phpunit.xml.dist

Delete hidden files ".*"

Delete folder "bin"

Delete folder "vendor"

Delete composer.json

Copy into this folder, and update this readme to cover any changes.
