Activity Flow Control Established

Fixed a curious situation in which opening the Email or Cancel
Appointment activities and hitting the back button would cause an
outdated version of Appointment List to display. This is because,
previously, when an intent was made to another activity, the new
activity was opened and the old one was left running in the background.
Hitting back caused the background activity to be displayed. Now,
hitting back intents to the previous activity, so all information in
Appointment List is accurate.