Make settling up easier #66

Problem

After a trip, people have to eyeball the balances list and figure out who
should pay whom to even things out. It's slow and error-prone with more
than 2-3 people.

Desired outcome

Settling up should be easier. Not sure exactly what that looks like yet -
maybe a clearer summary, maybe something else.

Acceptance criteria

(not provided - please ask)

Out of scope

(not provided)