AB test using a remote host serving the Experiments API

If AB tests were hosted remotely this is what it might look like. Its using a modified auth-server for this test but it would certainly **not** live there in real life.

`ab.js` is the browserify-ed bundle of https://github.com/dannycoates/fxa-content-ab

See https://dcoates.dev.lcip.org

f? @shane-tomlinson @zaach et al.
Ah, now I see what's going on. Not sure if it would help performance if the script was bundled and experiments were loaded separately. Maybe a later optimization we could make.