getUserContacts gets paged facebook friends

When your contact/friend list is long enough, we have to use the pagination method included in every facebook returned value.

Tested with Facebook Graph API v2.1. If the returned results are different in previous versions, there should be no difference (the commit always checks the fields exist inside the returned array.
Merge pull request #301 from neverbot/fb-paged-friend-list

getUserContacts gets paged Facebook friends