Add missing PHPDoc tag, update readme, more use of mbstring extension

7.0.1

Add missing PHPDoc tag, update readme, more use of mbstring extension

Nested subexpressions

• Infinitely-nested subexpressions
• Better parsing of arguments
• New concat helper to concatenate strings together
• Ensure compiler is initialised properly on each compile

SafeString support

This release adds support for SafeStrings in Helpers:

use MattyG\Handlebars\SafeString;
$handlebars->registerHelper('safehelper', function($value) { return new SafeString($value . '&BAZ'); });
$template = $handlebars->compile('{foo}} {{safehelper 'BAR'}}');
echo $template->render(array('foo' => 'FOO'));
// result: 'FOO BAR&BAZ'