Improve unit tests

Work in progress do not merge.

Just if you want to see what I modify in your library to improve tests.
- I add SimpleCov to see more with code coverage.
- I remove username in user class, this data is never return by the API, l_name is always empty, only f_name is returned to identify the user name.
Im not sure why you use this syntax. Even rubocop prefers to use the following syntax:

```
something.
  action.
  action2.
  action3
```