Bump to v4.0.0.

toLower.js

@@ -0,0 +1,27 @@
+define(['./toString'], function(toString) {
+
+  /**
+   * Converts `string`, as a whole, to lower case.
+   *
+   * @static
+   * @memberOf _
+   * @category String
+   * @param {string} [string=''] The string to convert.
+   * @returns {string} Returns the lower cased string.
+   * @example
+   *
+   * _.toLower('--Foo-Bar');
+   * // => '--foo-bar'
+   *
+   * _.toLower('fooBar');
+   * // => 'foobar'
+   *
+   * _.toLower('__FOO_BAR__');
+   * // => '__foo_bar__'
+   */
+  function toLower(value) {
+    return toString(value).toLowerCase();
+  }
+
+  return toLower;
+});