Use HTTPS where possible

[pr0gramista]

If you don't, the live example won't work on some browsers fe. Chrome.

Mixed Content: The page at 'https://t00rk.github.io/bootstrap-material-datetimepicker/' was loaded over HTTPS, but requested an insecure stylesheet 'http://fonts.googleapis.com/css?family=Roboto:400,500'. This request has been blocked; the content must be served over HTTPS.