- changes to marketplace constructor
- we no longer have _marketplaceTotals
- timestamps have their own type now
- freeSlot no longer takes payout addresses
- slot state 'Paid' no longer exists
- freeSlot can be invoked more than once now
- a failed request no longer ends immediately
This commit adds CVL rule that formally verifies the state changes of
any given request in relation to the functions of the contract that can
cause them.
Closes#128