Get media URL from new end point.

Hi!

Thanks a lot for your work letting XBMC users enjoy NRK! As you probably already have noticed some changes happened to the old API during the past week. I meant to let you know beforehand, but due to internal movement we had to release it a bit earlier. Anyways I've created a tiny PR illustrating the change. We are letting the endpoint http://nrk.no/serum/api/video/{id} live for now but it's only a re-direct to the preferred http://v7.psapi.nrk.no/mediaelement/{id} endpoint.