fix controls in responsive themes

I have been seeing the controls on the front-end venue Google Map appearing to be corrupt in some themes, including WP's own 2013 theme. Turns out that many responsive themes style images globally with `img { max-width: 100%; height: auto; }`. However, this breaks embedded Google Maps. See, for example:
http://vuknikolic.me/2012/04/02/twitter-bootstrap-and-google-maps-v3/

EO needs to ensure that controls aren't displayed in a corrupt-looking way by clearing the `max-width` property within the scope of the Google Map's enclosing element on the front end.

Cheers, Christian