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.
This is a bad hash formatting. Prefer:

```
{
  "key" => "value"
}
```