Use the official Google API Client

Hi,

I've made some little changes to make use of the official Google PHP API Client instead of the outdated one (`bitgandtter/google-api`).

However, the install problem described in Issue #4 remains in my environment. I've to include the two requirements in my main composer.json:

```
"google/apiclient": "~1.0.0-beta",
"thujohn/analytics": "dev-master"
```

Best regards

Marcus