Merge pull request #19 from interstroom/master

Dutch translations
Update SonataClassificationExtension.php

Fixed 'inversedBy'. Was NULL and causing Invalid Entity errors
Merge pull request #20 from rylorin/master

Update SonataClassificationExtension.php
Fix managers to use BaseEntityManager

Fix managers

Fix managers
Merge pull request #21 from eko/managers

Fix managers to use BaseEntityManager
Add APIs for Category, Collection and Tag models

Fix managers

Fix deletion exceptions to be catched by FOSRestBundle

Update composer.json
Merge pull request #22 from eko/api

Add APIs for Category, Collection and Tag models
Fixed typos
Merge pull request #23 from pborreli/typos

Fixed typos
Added CONTRIBUTING.md file
Merge pull request #27 from Bladrak/contributing

Added CONTRIBUTING.md file