Whitespace
Typo in Estimate->update() method
Adds the ability to edit an estimate.

Closes #8.
Improve User->update() method
Add the abilty to edit users in the system.

Work on #9.
Allow password reset for users.

Closes #9.
Create the Invoice class.

Work on issue #10.
Amend `printed` column name in invoices table
Add the ability to list invoices.

Closes issue #10.
Merge branch 'master' into demo

Brings the demo branch up to date with master