Update documentation to include committer add format

## Feature Request
#### Description
Presently the documentation doesn't tell the user what to add after `guet add`.

#### Example
Documentation and guet help should show the user to write out the following:

**`guet add`  _initials_  _"Full Name"_  _email@mail.com_**

### Note:
It could also be helpful to show examples of how to use guet set: **`guet set` _ac cb_** for example
