Google maps shortcode

Original report from editorial:

```
Paste in <iframe src="https://mapsengine.google.com/map/u/0/embed?mid=zI1R9jeSBMgk.kSy-zcZPHrw8" width="100%" height="550"></iframe>

Get [googlemaps https://mapsengine.google.com/map/u/0/embed?mid=zI1R9jeSBMgk.kSy-zcZPHrw8&amp;w=100&amp;h=550]

Note the width=100 pixels instead of 100% responsive
```

All of these shortcodes should probably have unit test coverage.
Could this be changed to `preg_match( '@google\.[^/]+/maps?@', $content )` instead?