Basic support for ledger importing w/ persistence.

Ledgers can now be imported and persisted.

Example:

```
purchaser name	item description	item price	purchase count	merchant address	merchant name
Snake Plissken	$10 off $20 of food	10.0	2	987 Fake St	Bob's Pizza
Amy Pond	$30 of awesome for $10	10.0	5	456 Unreal Rd	Tom's Awesome Shop
Marty McFly	$20 Sneakers for $5	5.0	1	123 Fake St	Sneaker Store Emporium
Snake Plissken	$20 Sneakers for $5	5.0	4	123 Fake St	Sneaker Store Emporium
```
Added Zeus support....for speed son!
Make Rubocop recommended modifications.