Add HTTPS support for download URLs

[abitrolly]

HTTPS on https://kompose.io/ is broken. Because GitHub doesn't support HTTPS on custom domains - https://stackoverflow.com/questions/42172216/is-it-possible-to-use-https-ssl-on-github-pages-sites-with-a-custom-domain - one of the solutions is to use Netlify - https://www.netlify.com/docs/ssl/

[surajnarwade]

Thanks @abitrolly :) for the useful information.
cc: @cdrage

[fejta-bot]

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[cdrage]

/remove-lifecycle stale

[abitrolly]

This now can be fixed properly by projects admins https://blog.github.com/2018-05-01-github-pages-custom-domains-https/

[fejta-bot]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.

If this issue is safe to close now please do so with /close.

Send feedback to sig-testing, kubernetes/test-infra and/or fejta.
/lifecycle stale

[abitrolly]

Now there could be a redirection from http://kompose.io/ to https version.