This brings this codebase up to speed with current JS standards.
- Moved tests to an updated version in test/feature_extractor.js (based
on test/compress.js, which in turn was evolved from test/run-tests.js)
- Update test/feature_extractor/*.js files to use valid JS syntax (
multiline strings in JS template strings)
- Drop use of deprecated sys methods (using console instead).
Upstream changes supporting the development process (.github/ and
CONTRIBUTING.md) were not included in this merge.
