If your just using the google maps (or any other embed such as youtube, soundcloud etc.) IFRAME embed you can make it responsive by simply adding this to your CSS.
iframe, object, embed{max-width: 100%;}
If your container/theme is responsive this will work great. Essentially this will work with ANY iframe and not just limited to google maps. But keep in mind if you have other iframes on your site they will as well become responsive.
