Fix GeneratePermutations so that it actually returns the permutations instead of logging them + add Jest test.

Backtracking/tests/GeneratePermutations.test.js

@@ -0,0 +1,14 @@
+import { permutations } from '../GeneratePermutations'
+
+describe('Permutations', () => {
+  it('Permutations of [1, 2, 3]', () => {
+    expect(permutations([1, 2, 3])).toEqual([
+      [ 1, 2, 3 ],
+      [ 1, 3, 2 ],
+      [ 2, 1, 3 ],
+      [ 2, 3, 1 ],
+      [ 3, 1, 2 ],
+      [ 3, 2, 1 ]
+    ])
+  })
+})