Switch protocol-relative URLs to SSL for CloudFlare CDN assets

I use flamegraph in conjunction with rack-mini-profiler extensively to test our app locally, with flamegraph output saved to disk (via cURL, via Save As ..., etc).

This worked amazingly well with rack-mini-profiler 0.1.26, but breaks on HEAD of the extracted flamegraph gem.  CloudFlare CDN assets look like: 

    file://cdnjs.cloudflare.com/ajax/libs/jquery/1.9.1/jquery.min.js

This fails.

Not sure how you feel about this, but always using https://cdnjs.cloudflare.com/ajax/libs/jquery/1.9.1/jquery.min.js would work in all protocols (http, https, file) :+1: