message: Use secure URLs in README
  Saves a redirect from HTTP -> HTTPS each.
  [ci skip]
diff: ### Resources
  -* Homepage: <http://opencv.org>
  -* Docs: <http://docs.opencv.org/master/>
  +* Homepage: <https://opencv.org>
  +* Docs: <https://docs.opencv.org/master/>
  * Q&A forum: <http://answers.opencv.org>
  * Issue tracking: <https://github.com/opencv/opencv/issues>
  