PHP port of Markup.js

The test suite has also been ported, with some changes to take into account differences between PHP and JavaScript. Specifically:

• PHP has no equivalent of undefined
• PHP can not call methods on primitives (like strings, ints)

In general, JavaScript's behavior is maintained, for example true + " " + false in JS evaluates to "true false", whereas in PHP it would evaluate to "1 ".

Requires (at least) PHP 5.4.

To use:

<?php
require('Mark.php');
use Markup\Mark;
$context = [
	'name' => [ 'first' => 'John', 'last' => 'Doe' ],
];
$template = "{{name.last}}, {{name.first}}";
$result = Mark::up($template, $context);
?>