Fixed a bug in -fetchPostsStarredByUserWithID: completion:

This function was trying to fetch a user's favorite posts list using "posts/%@{userID}/stars" when the correct is "users/%@{userID}/stars". Fixed :)
Merge pull request #19 from rafaelc0sta/master

A fix for a bug in "-fetchPostsStarredByUserWithID: completion:" (ANKClient+ANKPost)