keybase prove web command

Hello,

When someone tries to prove a website he owns using the keybase.txt file there is issue. If the hosting provides both protocols http and https it automatically selects the https one. Probably this is good for the 99% of the time. But there are time where the user doesn't want the https version. There should be a parameter to explicitly select the http protocol.

Check this website: http://hargikas.bitballoon.com/ works fine but then https://hargikas.bitballoon.com/ there are issues in https.

Thank you,
Harry

Start with the `keybase prove web` command and trace how it selects HTTP versus HTTPS when checking a site's keybase.txt file. Define how an explicit HTTP selection should be passed and verify that the example HTTP-only-preferred case succeeds without breaking the default HTTPS behavior.

Written by the indexing model from the issue text.