Refactor mvc framework

• Based on MVC, project was separated into 3 folders: templates, handlers, models.
• Basic functions supporting handlers and models were grouped into utility.
• Four service were provides: user, post, comment, like.
• Each service was supported by one corresponding handler and one model.
• Documentation was rewritten based on setup and features.

First usable version of multi-user-blog

• Multi users can signup/login/logout.
• Login users can add/edit/delete their own posts.
• Login users can comment on any post and edit/delete their own comments.
• Login users can like/unlike others' posts.
• Any users can read posts and comments.