Person.favorites feed only return 20 items

[kabniel]

Person.favorites inherits from the Feed class which relies on links['next'] to navigate through a feed's items list, but the pump.io API doesnt add the needed links for the favorites feed, see pump-io/pump.io#812

[kabniel]

I added a work around for this issue, using offset incrementation instead of next/prev links for Favorites feed navigation.