Add QUnit to tests

- Migrated tests to QUnit.
- Kept the diff table at the bottom to also show what the results look
  like
Refactor test results table

- Fix spacing issues
- Refactor table and create helper function to populate results table to
  remove duplicate .getElementById() calls
Renamed demo.html to tests.html and updated CSS

- Renamed demo.html to tests.html
- Added CSS for results table so it isn't so ugly