change flickr api endpoint to use https

the flickr api went ssl-only on june 27th, read more:
http://code.flickr.net/2014/04/30/flickr-api-going-ssl-only-on-june-27th-2014/
Merge branch 'flickr-https' of github.com:lefant/oauthd into lefant-flickr-https
Merge branch 'lefant-flickr-https' into develop
Merge branch 'develop' of github.com:oauth-io/oauthd into develop