Provide fine grained control over the appearance of <MUIPlacesAutocomplete>

[Giners]

<MUIPlacesAutocomplete> composes several elements/components to provide the functionality/appearance that it does. Consumers should be able to modify the functionality/appearance of <MUIPlacesAutocomplete> and in a way that is consistent with how Material-UI works (see https://material-ui-next.com/customization/overrides/) to meet their business needs/requirements.

My first thought is to using styling techniques. These resources can be used as starting points for providing a solution:

• https://material-ui-next.com/customization/overrides/
• https://material-ui-next.com/customization/css-in-js/
• https://github.com/mui-org/material-ui/blob/v1-beta/docs/src/pages/customization/RenderProps.js
• https://github.com/mui-org/material-ui/blob/v1-beta/docs/src/pages/customization/StyledComponents.js

This request was inspired by the discussions in #28.