Use Composer for Parser dependencies, update Mustache.

 * Composer packages are currently available for Mustache, Twig and Smarty. Recommend using those instead of the old "dump it in vendor" strategy.
 * Update Parser config now that vendor libraries are handled by the Composer autoloader.
 * Remove the outdated Mustache library.
 * Update Mustache View to be compatible with Mustache.php v2.x, which is the version available on Packagist.

Fixes #61