Migrated tests to jest

Used jest-codemods to migrate, will have to pass everything by hand before we can merge.

test4/mapKeys/mapKeys.test.js

@@ -0,0 +1,9 @@
+const expect = require('expect');
+const mapKeys = require('./mapKeys.js');
+
+test('Testing mapKeys', () => {
+  //For more information on all the methods supported by tape
+  //Please go to https://github.com/substack/tape
+  expect(typeof mapKeys === 'function').toBeTruthy();
+  expect(mapKeys({ a: 1, b: 2 }, (val, key) => key + val)).toEqual({ a1: 1, b2: 2 });
+});