Merge pull request #2 from devstarter/contents

Refactor categories
Merge branch 'master' of https://github.com/devstarter/ii into contents
added next and previous category for root category in the contents
update ContentsHelper
Merge branch 'master' of https://github.com/devstarter/ii into contents
fixed wrong commit
Merge pull request #87 from Ekvi/contents

Contents: added next and previous for root category