Modal does not honor provided CSS class in "className" property

### Description
CSS class provided in Modal "className" property does not have any effect.

Currently bypassing this issue by directly manipulating underlying "fundamental-style" CSS property of Modal.

`.fd-modal{
    max-width: none!important;
}
.modal-demo-bg{
    width: 90%;
}`


### Versions
**fundamental-react:** 0.7.1
**fundamental-styles:** 0.3.0
