merge
Merge branch 'master' of git@github.com:COMP-3350-Group-6/Project.git
Added the Receipt Screen class to the GUI that prints out the users
tranasction.

error proofed so that the user is not able to go to the booking screen
without finding and selecting a valid flight.
Merge branch 'master' of git@github.com:COMP-3350-Group-6/Project.git