Creating a Dev branch for the project
Added ability to view 'unpaid' invoices.
Form styling.
Formatting/links: updated forms to add consistency and language clarity (e.g. link titles/names).
Payment list: added customer name to the list; updated 'delete' link title.
Customer page - invoice list: linked invoice-id to invoice page
Added method stub for calculating if the invoice is overdue.
Customer page: invoice list - added invoice notes.