Support for nested parameters

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #46, #36, #35
| License       | MIT
| Test repo        | https://github.com/lucascourot/test-multi-level-params

This PR provides a support for nested parameters. You can check out the [demo](https://github.com/lucascourot/test-multi-level-params) to play with it.