Fix #13 and #14: Customers delete and Customers add

- Customer add now works
 * Removed use of id in index.php
- Customer delete now works
 * Added additional include file
- Added Customer_Test for CRUD tests
feature/sales: Added CRUD tests

- Adding default branch makes the api consistent with the FA ui.
- This is necessary for testing of the sales api
Merge pull request #21 from cambell-prince/feature/Sales

feature/sales: Tests and enhancements for sales api