Added Flickr sharer service

[Muppets]

Modified Config.h to include Flickr API keys

[bluesuedesw]

Big ups to Muppets! Thanks so much for sharing. This works great. Couple of tips for future users:

1 - This requires the CFNetwork.framework
2 - One needs to setup the flickr app as a "web service" on the flickr authentication flow settings, and enter in your app's custom callback URL scheme.
3 - make sure you define and create the same URL scheme in your apps info.plist. It can be as simple as yourapp://flickr

[Eric-Wright]

Great work, Muppets! And thanks to bluesuedesw for the clarification, that helped me get this working quickly.

I noticed that LFSiteReachability.h/.m and NSData_LFHTTPFormExtensions.h/.m were unused, so I removed those files from my local copy.

I also modified SHKFlickr -sendPhoto: to not set the is_public flag. For my application, I want new photos to inherit the user's default sharing settings, rather than forcing all new photos to be private.

[Muppets]

Thanks Eric for your feedback. I've made your changes and pushed up a new commit.