All Done - Homework Planner

Invalid date

Feature changes:
- The assignment will automatically save after pressing back. New cancel button instead of "save" button.
- New "complete" option in detail page's menu. (For tablets that won't display the orange complete button)

Fixes from previous versions:
- Edit class page had incorrect buttons for saving
- Feedback button in "Help" page

Thank you to all the users who gave me feedback and suggested improvements in the review!

New features and updates to come! Working on UI improvements!