Subscription Contract

[Alonski]

Need to write contract for subscription...
This will be tough

As mentioned in #21:
The contract we actually need it something like this:
Bobs CoinVault:
Functions:

• Receive coins from Bob to be used in Vault
• Setup subscription to Address xyz
  -- When called with an amount, an address, and timespan in days. Immediately sends out the first amount to the address and schedules itself to call itself again in timespan days.
• Cancel subscription to Address xyz
• Return coins to Bob by request.