Modularize master branch.

_isMaskable.js

@@ -0,0 +1,14 @@
+import coreJsData from './_coreJsData.js';
+import isFunction from './isFunction.js';
+import stubFalse from './stubFalse.js';
+
+/**
+ * Checks if `func` is capable of being masked.
+ *
+ * @private
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `func` is maskable, else `false`.
+ */
+var isMaskable = coreJsData ? isFunction : stubFalse;
+
+export default isMaskable;