Resolve HTTP redirects to avoid https problems

Note:
mplayer cannot handle https urls.

Previous situation:
This has already been partially covered by changing the protocol of the
url to http. Soundcloud sometimes uses 302 redirects, that still make
the converted url point to a https resource, that mplayer can't work
with.

New situation:
The player now resolves redirects before changing the protocol in the
url. This ensures that mplayer gets the final http resource and is not
being redirected to another https resource.