- Strict checks throw when `process.env.XMLDOM_ASSERT_STRICT` is truthy,
  otherwise they are only logged when they fail
- `assert.skip(...)` can be used for failing assertions (and need to be removed when they no longer fail)
- tests for `assert` and `assert.skip` are part of `npm run test`

Renamed the qualifying `.js` files to `.vows.js` to simplify filtering.

The `assert.throw` fails since the code no longer throws exceptions when parsing fails.

The primary purpose is to make it absolutely clear
that the return expression spans multiple lines,
should be a little more consistent with
Prettier formatting.