Bump to v4.10.0.

_castFunction.js

@@ -0,0 +1,15 @@
+define(['./identity'], function(identity) {
+
+  /**
+   * Casts `value` to `identity` if it's not a function.
+   *
+   * @private
+   * @param {*} value The value to inspect.
+   * @returns {Function} Returns cast function.
+   */
+  function castFunction(value) {
+    return typeof value == 'function' ? value : identity;
+  }
+
+  return castFunction;
+});