Add "place" and "coordinates" to Tweet class

Implemented deserializing of geolocation information from twitter responses and added "place" and "coordinates" to Tweet class.

Changes are kept minimal and I've avoided using deprecated classes. A class named Coordinates were implemented alongside with its JsonMixin and Deserializer, An attribute of type coordinates were added to Tweet. 

Changed the behavior of "boundingbox" property to support the latest changes in Twitter API. boundingbox were a list of points, corrected it to be the type of Geometry

Added place attribute to Tweet class and wired necessary deserialization. 

Added necessary tests