Tweaking README. Too long a name...
Changing contributor name. Minor thing
Adding ID and updated_at attributes for the User entity. Related to #37

More work to come to this entity. Some basic things are still missing.
Adding getURL() and toString() methods for User entity. Related to #37
Little change to class description doc
Documenting the User class. Related to #37
Adding getURL method to the Project class.
Adding interface to serve as a base for every GH API object representation in Groundhog
Implementing GHEntity interface methods in Organization. Related to #37
Adding toString() method to Organization. Related to #40