Guestbook edit message

- Limit post message (10 letters), validate with Django Formview
- Owner and administrator can edit message
- Show updated_by and updated_date on view
Guestbook edit message

- Limit post message (10 letters), validate with Django Formview
- Owner and administrator can edit message
- Show updated_by and updated_date on view
Rebase to feature/delete-message
fix conflict

fix conflict
Fix comment

- Use method get_greeting_by_id
- Admin can edit and delete, owner can edit
- Use one url to handle Edit request
Fix comment

- Owner can edit greeting
Fix comment

- Use “cls” instead of “Class name” when call the internal method
Merge pull request #12 from nhathv/feature/edit-message

Merged pull request #12 Feature/edit message