Fix parameters in Safari on macOS and iOS

[ColinNg]

The fix is to read the form data which appears after \r\n\r\n (HTTP POST data was verified with WireShark).

[ColinNg]

This is a fix for https://github.com/tayfunulu/WiFiManager/issues/9

I apologize I don't know how to tag an Issue number in my commit, so I reference it now in a PR comment.

[fluviusmagnus]

Thanks. This fix is really helpful.