v4.0.0

Replaced the Android Location Manager approach with the Google Play Location Service one (used by Google Maps) as there are a lot of known issues with the Location Manager and it's not the recommended approach for getting a location on Android.

Fixed issues #42, #52, #62, #64 and #69.

Breaking changes:

• isEnabled returns 'Promise' instead of 'boolean'
• updateDistance option is not available for android anymore, use updateTime instead. A hint from Google: update interval of 5000 milliseconds (5 seconds), causes the location provider to return location updates that are accurate to within a few feet.