Change the POST request to a GET one for a static question.mark.html to improve compatibility on nginx servers

Currently, QuestionMark does a POST request to get the content of question.mark.html.

This fails gracefully on nginx servers, as a POST request against a static file will return a 405 non authorized error.

I use the adverb gracefully, as this won't provide any JavaScript error.

A GET request seems more appropriate, as the question.mark.html content is static.