Fixes #582 - adds Google Maps API key

Fixes #582 - adds the ability to set a Google Maps api key when loading
the Google Maps APIs. If no API key is set the maps APIs load
anonymously from google.
Okay, along those lines we should be consistent across all our API key/token terminology, which means `GOOGLE_TRANSLATE_API_TOKEN` should become `GOOGLE_TRANSLATE_API_KEY` and `OHANA_API_TOKEN` should become `OHANA_API_KEY`, right? I'll just update for maps here and open an issue for the others.