Make \Parable\Http\Response HTTP/2 ready

[FaaPz]

My production environment uses HTTP/2, so I suggest something like this to make it future-proof:

header("{$_SERVER['SERVER_PROTOCOL']} {$this->getHttpCode()} {$this->getHttpCodeText()}");

http://php.net/manual/en/function.header.php#92305

And please do throw away that array of HTTP status codes. It's not needed, because you can use http_response_code(). http://php.net/manual/en/function.http-response-code.php#116880

[devvoh]

Will be fixed in 0.12.5.

Not the array, though ;)

[devvoh]

Should be fixed in 0.12.5. Reopen if it requires fixes!