Coverage for direct links.
The direct link won't work because it will have the wrong auth anyway but this will at least end up with the right API call.
Add check to verify token was received.
Update headers sent to content API.
Add availability check for videos to resolve last part of #472 where only SD version is available.
Cover edge cases that shouldn't ever happen but probably will sometime.
Also included Imgur changes to cover similar situations of malformed/redirected links.
API seems to return incorrect signature value when sending header. Other fixes seems to have worked temporarily but have stopped working so they're removed.
Soulsuck24