2.2 Guestbook django class-baseview

- Using: TemplateView
Fix comments

- Using google api memcache
- Using BaseCreateView for method sign_post
- Order import module
- Remove model = Greeting
Fix comment

Use object View instead of BaseCreateView to handle Post method
Merge pull request #3 from nhathv/feature/class-basedview

Merged pull request #3  Guestbook django class-baseview