Completed CRM tutorial
Added print_main_menu method to prompt user to type a selection
Added main_menu and call_option methods - Added case to call method based on user's selection
Added add_new_contact method - the user can now type in first, last name, email and notes
Added method to modify existing contact - Added class Contact and Rolodex to create a database
Added a class method run - A new instance of CRM is created when calling run on crm
Added external files - using require_relative to load data from contact.rb and rolodex.rb