Require GPS to be enabled

[13rac1]

Since this app doesn't do much without GPS, we need to make sure it's enabled. We can use other location detecting methods in the future, but GPS is required for now.

[13rac1]

maybe

String GpsProvider = Settings.Secure.getString(getContentResolver(),
Settings.Secure.LOCATION_PROVIDERS_ALLOWED);

if (GpsProvider.toLowerCase().indexOf("gps") >= 0 ) {
    return true;
} else {
    return false;
}

[multidynamic]

The MainActivity currently enables the Listen button for certain criteria, we can simply add whether Location services are set on to that criteria.

We could also send an intent to the settings app to prompt the user to enable it.

And, maybe use one of these icons: http://google.github.io/material-design-icons/

[multidynamic]

If it is ever decided to use the fusedLocation branch, an update to play services 7 provides a call to prompt the user to authorize location without leaving the app.