Request::DOWNLOAD method is preserved in redirect

When I make DOWNLOAD request, follow redirect and get response with Location header, I get an error:
`Kdyby\Curl\InvalidStateException: File '.headers' not readable. in ..../Kdyby/Curl/FileResponse.php:174`

I've solved the problem with preserving Request method in Curl\Request::followRedirect().

Now everything works fine.

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I didn't write tests because it's impossible do that.