Revert "Only cancel cancellable shipments."

This reverts commit d870c4e316e3aad6f63c728d224f6a16d4edde57.
Fix form fields.
Bootstrapping Email HTML templates.
Fix email specs.
Add test rake task and refactor layout.
Cleanup unused premailer/ink stuff.
Cleanup templates.
Fix broken spec due to LineItem#options= not being able to assign target_shipment.