Added OSKSaveToCameraRollActivity to Overshare sample project in order for it to build properly.
Merge upstream.
Allow Facebook photo-only post.

Fix: Facebook activity did not let the user post a photo to Facebook
without entering any text.
Merged Xcode Project file from upstream
Merge pull request #57 from kkarayannis/master

Merge pull request #57.
USE_UNDOCUMENTED_ANIMATION_CURVE