Add attachment managers interface.
Add PostMetaManagerInterface.
Add more interfaces.
Add option manager.
Should be implements instead of extends.
Add TermManagerInterface.
Implement cache in option manager.
Bug fix.
Cache minor fix.
Implement TagManager.
Implement attachment manager.
Add TODO.
Implement Attachment Manager
Merge pull request #3 from luiges90/model-managers

Implement Attachment Manager
Complete Post Manager
Attachment: sort in menu order
Model: add Post Manager Service
Implement Post Meta Manager
Fix typo
Twig: implement attachment twig ext