Add initial test files from lodash v4. (#4172)

* 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.

test/matches.js

@@ -0,0 +1,32 @@
+import assert from 'assert';
+import lodashStable from 'lodash';
+import matches from '../matches.js';
+
+describe('matches', function() {
+  it('should not change behavior if `source` is modified', function() {
+    var sources = [
+      { 'a': { 'b': 2, 'c': 3 } },
+      { 'a': 1, 'b': 2 },
+      { 'a': 1 }
+    ];
+
+    lodashStable.each(sources, function(source, index) {
+      var object = lodashStable.cloneDeep(source),
+          par = matches(source);
+
+      assert.strictEqual(par(object), true);
+
+      if (index) {
+        source.a = 2;
+        source.b = 1;
+        source.c = 3;
+      } else {
+        source.a.b = 1;
+        source.a.c = 2;
+        source.a.d = 3;
+      }
+      assert.strictEqual(par(object), true);
+      assert.strictEqual(par(source), false);
+    });
+  });
+});