The master branch has been in flux for a pretty long time, so leaving
the broken npm scripts and messages in CONTRIBUTING.md doesn't make
sense and has been confusing to contributors. This commit removes broken
npm scripts and removes all unnecessary dependencies for now.
* Install test dependencies.
* Add initial test files.
These files were created using a simplistic AST manipulator using `recast` to
preserve formatting. There's bound to be a huge chunk of errors, but this serves
as a good start. QUnit was replaced with Mocha, with ES2015 imports running via
`esm`.
As far as possible, QUnit-specific syntax has been replaced with Mocha's
`describe` and `it`, while the native Node.js `assert` module is used for
assertions. Files in the `test` directory ending in `.test.js` will be treated
as test files.
* Add initial passing files to test run.
