Refactored method that retrieves the user's information and implemented jUnit test for it
Moved User-related information in the corresponding UserInfo class. Created a constructor that creates a UserInfo object from a JSON object. Removed  unnecessary fields and methods from the User class.
Implemented jUnit test for User.about method and improved it
Moved Exception class and Enums in the corresponding packages
Merge pull request #40 from RaulLepsa/master

Code improvements and refactoring regarding User and UserInformation