Master

See [original pull](https://github.com/kellydunn/golang-geo/pull/9)

golang-geo shouldn't panic when there are no results returned from Google geocoding API (ie. when the address is invalid).

I used the "status" message from the Google API as the error message returned (ZERO_RESULTS).

Finally, you need an additional env variable to run the tests, `GO_ENV=test`. I added that to the readme.

Please let me know if there's anything I need to fix up!

Cheers ~