Updated OAuth urls to https

Flickr recently enabled Strict-Transport-Security (HSTS) on their
backend, which transparently redirects http requests to https. As
result, OAuth signatures from redirected calls will be invalid, as the
base string from which they're generated still contains the string
"http" rather than "https". This patch resolves this issue by pointing
directly at https for OAuth.
Merge pull request #27 from JBLatenight/master

Updated OAuth urls to https