Changed endpoint urls to https as it is required by the Flickr API

This PR changes the API urls  from http to https as this is the only supported way of using the Flickr API soon (http://code.flickr.net/2014/04/30/flickr-api-going-ssl-only-on-june-27th-2014/). Otherwise each API Call fails. I provide this PR, as the Flickr page points to your Repo, so it should work without changes.

Philipp