Bug Fixes for UIImageView Extension

All issues associated with this milestone can be found using this filter.

Added

• Tests around the UIImageView extension usage with redirect URLs.
  • Added by Christian Noon in regards to Issue
    #15.
• Tests around the UIImageView extension usage with duplicate image requests.
  • Added by Christian Noon in regards to Issue
    #17.

Fixed

• Issue where UIImageView extension did not support redirect URLs.
  • Fixed by Robert Payne in Pull Request
    #16.
• Issue where duplicate image requests were cancelling the active image download
  in the UIImageView extension.
  • Fixed by Christian Noon in regards to Issue
    #17.