Also deal with PNG images
Increase the time between API calls

This is in the hope of avoiding the 403 errors that we sometimes get.
Change the host used for API requests

This change is required by The Guardian, as is a new API key:

  http://www.theguardian.com/info/developer-blog/2014/jul/17/introducing-the-content-api-v2?CMP=
Use /usr/bin/env in the shebang line