Point to new quickbooks gem and rename namespace

Previous Quickbooks module here is now called QBIntegration to avoid
conflicts with the quickbooks gem we're going to use
Couple tweaks to test auth in v3
Move auth stuff to its own class
Creates factory for product:new message
Creates /product_persist for importing products into Quickbooks
Let QB::Integration deals with basic stuff only

Both orders and products services can extend from this class
Updates Quickbook calls for product/account to V3
Creates services to wrap quickbooks api calls for Item / Account
Reworks ProductImporter using new specs
Makes Item service more generic
Creates Service::Base and specs for Service::Item
Adds tests for ProductImporter
Start porting order import to quickbooks v3 api (WIP)

We need to get this PR merged https://github.com/ruckus/quickbooks-ruby/pull/10
to make changes here work
Adapt to new Service::Base api
Put Service::Base#create_model as a public method
Build customer find or create
Add first cassete to sales_receipt persistence request

the persistence process should take a while
Move sales receipts lines to its own object
Add Service::Item#find_or_create_by_sku
Create items on the fly when doing sales receipt