Noteboard

Changes

1. Removed config system.
2. Reimplemented interactive mode with `cmd` library and `prompt-toolkit`.

New Feature

Interactive Mode

* view live changes of all boards
* modify multiple items & boards at a time
* more convenient and dynamic

Changes

1. Changed item mark from small dot `•` to big blue dot `●`.
2. Bolded and removed background highlight of the initial help text ``Type `board --help` to get started``.
3. Underline board titles.
4. `board` will now display day difference of each items in the format of `{diff}d`, e.g. `1 ● item1 1d`.

**Initial Release**