add initial failing test for Customer

also added minitest model task to default minitest rake task and
told guard to watch the test/models directory
add customer class

basic 'test' (not a test per se, but did the job of blowing up) now passes
failing test - let's look at data in the table

I decided to give the Customer model a name attribute (refering to
customers by id only would be frustrating and error prone). Adding a
test for the name attribute invokes the `before` method in the test,
and rails complains that the customers table doesn't exist.
add migration for Customer table

(and fix brain splort in before method, lol...)
add test to check that name is required
add validation, tests pass again
add (failing) test for customer has_many users
add migration, association customer has_many users

dependent destroy
test now passes
add (failing) test for customer has_many sites
add association customer has_many sites

test passes
add (failing) test user belongs_to customer

drat! Did the customer_id migration out of order. Feh.
add association user belongs_to customer

setup inverse_of on associations, as well
add (failing) test, site belongs_to customer

when I make this test pass, I'll need to fix existing specs as well.
FAILING intermediate save, coupling from fixtures

Existing rspec tests all fail due to a single problem with
the fixtures. The minitest design has been handling the same
structure without breaking a sweat.
integrate Customer model (+ views), reclaim specs

Once I wrapped my head around the combination of fixtures and rspec
I got back to humming along.

I updated the README.md with notes about where the project is and
what I'm planning on next, but the short version is that I've got
Customers integrated, with Sites belonging to Customers, Customers
have many Users, etc.

I haven't written cancel yet. I want to write an actual cancel method
that will destroy the Users and Sites associated with a Customer, but
not the Customer itself, because we need it for accounting purposes if
nothing else! Hmmm... we're already using state machine, oooohhh, yeah.

Yup, a status field for Customer, that's the ticket. It can serve as a
basic holder for Customers with suspended accounts (because they haven't
paid), too!
add Cancel design to README.md (duh)