Add support for inline styles

Inline styles can be useful when you want to change only a little bit
about a default map style, e.g. by merely removing clickable POI's from
the map.

Include in the map options

styles => $style

where $style is the JSON array containing your inline style, e.g.

$style='[{
    featureType: "poi",
    elementType: "labels",
    stylers: [
      { visibility: "off" }
    ]
}];';