Added support for 'captureOffsetAs' argument to parser
Added support for PHP __LINE__ magic constant
Added 'allowMerge' argument to parser to allow capturing AST nodes with only a name
Added support for PHP magic __FILE__ constant to grammar
Added support for PHP __FILE__ magic constant to interpreter
Added support for PHP magic __DIR__ constant to grammar
Added support for PHP magic __DIR__ constant to interpreter
Added support for magic PHP __DIR__, __FILE__ and __LINE__ constants to readme