add print_r dump operation to bin Script

While I wanted to explore a source code that have at least this source code 

```php
$this->$method();
```
I used for the first time the `bin/php-parse.php` script and try to dump contents of nodes with `--var-dump` operation.

It gave me too little info (for my point of view). See output as follow. 

    ==> var_dump():
    array(1) {
      [0] =>
      class PhpParser\Node\Expr\MethodCall#12 (2) {
        protected $subNodes =>
        array(3) {
          'var' =>
          class PhpParser\Node\Expr\Variable#13 (2) {
            ...
          }
          'name' =>
          class PhpParser\Node\Expr\Variable#14 (2) {
            ...
          }
          'args' =>
          array(0) {
            ...
          }
        }
        protected $attributes =>
        array(2) {
          'startLine' =>
          int(2)
          'endLine' =>
          int(2)
        }
      }
    }

I would like to have all details, so I've added a new operation called  `--print-r`, that gave me following output

    ==> print_r():
    Array
    (
        [0] => PhpParser\Node\Expr\MethodCall Object
            (
                [subNodes:protected] => Array
                    (
                        [var] => PhpParser\Node\Expr\Variable Object
                            (
                                [subNodes:protected] => Array
                                    (
                                        [name] => this
                                    )

                                [attributes:protected] => Array
                                    (
                                        [startLine] => 2
                                        [endLine] => 2
                                    )

                            )

                        [name] => PhpParser\Node\Expr\Variable Object
                            (
                                [subNodes:protected] => Array
                                    (
                                        [name] => method
                                    )

                                [attributes:protected] => Array
                                    (
                                        [startLine] => 2
                                        [endLine] => 2
                                    )

                            )

                        [args] => Array
                            (
                            )

                    )

                [attributes:protected] => Array
                    (
                        [startLine] => 2
                        [endLine] => 2
                    )

            )

    )