Bump to v4.0.0.

now.js

@@ -0,0 +1,19 @@
+/**
+ * Gets the timestamp of the number of milliseconds that have elapsed since
+ * the Unix epoch (1 January 1970 00:00:00 UTC).
+ *
+ * @static
+ * @memberOf _
+ * @type Function
+ * @category Date
+ * @returns {number} Returns the timestamp.
+ * @example
+ *
+ * _.defer(function(stamp) {
+ *   console.log(_.now() - stamp);
+ * }, _.now());
+ * // => logs the number of milliseconds it took for the deferred function to be invoked
+ */
+var now = Date.now;
+
+export default now;