Allow range requests

[MarcelloTheArcane]

Two options.

1. It happens at the gmusicproxy end (hardly likely, they are very slow on updates though there is an issue)
2. Create a service worker that proxies requests to media and returns range headers based on a cached file. We have an audiocache, not sure if service workers play nicely with vuex, or if it's possible to hijack it somewhere in between.