New features:
- Auto update local content when remote content is newer.
- Create new notebook (M-x leanote-notebook-create).
- Delete current notebook (M-x leanote-notebook-delete).
- Get current login user info (M-x leanote-get-user-info).
Bug fix & optimus:
- Fix leanote-extra-abstract function bug when content hasn't #.
- Optimization for http request action.