Transform protocol-less src to https instead of http

[danielbachhuber]

If we're provided a protocol-less URL, we can safely assume it supports https

See #107

[danielbachhuber]

@goldenapples #reviewmerge

[goldenapples]

I don't think we want to do this for all tags, do we? This might work for script tags, but an https iframe on an http page will cause problems with postmessage communication.

I think it would make more sense to store the url field as protocol-less if that's how it's provided to us.

[danielbachhuber]

This might work for script tags, but an https iframe on an http page will cause problems with postmessage communication.

Touche. Let's 🏈