Added fraction overlay to the game. Overlay will display the fraction
values of the selected roads and ask the player to submit the sum of
those fractions.

Players who submit the correct answer will be eligible for a bonus
if their route contains any structure that has not been delivered to,
or a fuel station.
Some changes have been made to how the bonus system works. Only
delivery locations are eligible for the bonus now, and the overlay
will only display when the user clicks on the vehicle to drive. If
the user wishes to skip the bonus process, they can click the
vehicle again to initiate driving. Otherwise, they input the fraction
sum and click on the submit box, and the vehicle will begin driving
after the calculations have been made.
Base bonus system is complete.