fix(SebmGoogleMap): allow styling via comp styles

[sebholstein]

With v0.8.0, styling the map via the styles setting
of a component was NOT possible any more:

@Component({
    selector: 'my-map-cmp',
    directives: [SebmGoogleMap],
    styles: [`
        .sebm-google-map-container {
            height: 300px;
        }
    `]
}

Fixes #162