First commit on fork
added tables but haven't deleted any from initial data dump
Backed out all migrations and re-migrated with null restrictions
removed all redundant columns from sales database
Revert "removed all redundant columns from sales database"

This reverts commit 98f90d0c23debc1bf01d76d52d6245efaf245442.
Commit to open new branch
added validations to models
put invoice frequency back in sales table
made minor adjustments to structure
data modelled how I want
employees view set up and set up framework for customers view
added url to customers table
added sales view but haven't fully populated it
finished non-core
Merge branch 'Attempting to merge'

Conflicts:
	app/models/customer.rb
	app/models/employee.rb
	app/models/invoice.rb
	app/models/product.rb
	app/models/sale.rb
	db/schema.rb