Fix PHP fatal error when maximumNestingLevel was reached.

[tanakahisateru]

When I created very deep block with Markdown syntax, I got a PHP error like as:

PHP Fatal error:  Call to undefined method cebe\markdown\tests\TestParser::rendert() in /.../Parser.php on line 202

t of ::rendert() is assumed as the first letter of 'text'. It comes from return ['text', $text];. But right block structure is [['text', $text]], I think. Is'nt so?

[tanakahisateru]

http://markdown.cebe.cc/try?flavor=default&text=-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+X%0D%0A

My problem is just above one.

[cebe]

awesome, thanks!