Provider version resolutions should be updated to provider

[guybedford]

Currently all provider version resolutions share the jspm.io version resolution, mostly just out of ease of implementation for now.

But the jspm.io version resolution isn't correct in the case where there is a build error as it will resolve the last known good build instead.

We should instead update individual providers to use their own version resolution hooks so there is only one origin, or at the very least directly get this info from npm.