Show payment fields for completed registrations which still have a balance
initialize payment amount to remaining balance
 - not calculated total due
only show minimum deposit text on the first payment
add informative text for subsquent payments
 - when registraiton is completed, but has balance, instruct user to pay balance
make sure minimum deposit check only applies on first payment
show confirm button for all non-completed registrations and when there's a balance that can be paid online
always show payment summary when payments are made online
 - but only allow payments to be made when remaining balance > 0
don't re-update a completed registration
 - just reload the page, it clears the cache and fetches the updated registration
just store payment in scope, not rootScope
payment summary fields
only show these fields
 - total cost as "Total Cost"
 - totalPaid as "Previous Payment(s)"
 - remainingBalance as "Remaining Balance"

Don't update these values based on the input payment amount for two reasons:
 - a console error is thrown when the amount text box is updated, related to the moneyFormat.  couldn't debug it.. it worked if the currentPayment.amount was part of the calculation to determine remaining balance, but not on its own in the payment field
 - most sites just don't do this. it's normal & expected to see what I owe during checkout and to not see that total change based on inputs.