Add options object to _.mixin. [closes #404]

dist/lodash.underscore.js

@@ -4235,27 +4235,32 @@
   }
 
   /**
-   * Adds function properties of a source object to the `lodash` function and
-   * chainable wrapper.
+   * Adds function properties of a source object to the destination object.
+   * If `object` is a function methods will be added to its prototype as well.
    *
    * @static
    * @memberOf _
    * @category Utilities
-   * @param {Object} object The object of function properties to add to `lodash`.
-   * @param {Object} object The object of function properties to add to `lodash`.
+   * @param {Function|Object} [object=lodash] object The destination object.
+   * @param {Object} source The object of functions to add.
+   * @param {Object} [options] The options object.
+   * @param {boolean} [options.chain=true] Specify whether the functions added are chainable.
    * @example
    *
-   * _.mixin({
-   *   'capitalize': function(string) {
-   *     return string.charAt(0).toUpperCase() + string.slice(1).toLowerCase();
-   *   }
-   * });
+   * function capitalize(string) {
+   *   return string.charAt(0).toUpperCase() + string.slice(1).toLowerCase();
+   * }
    *
+   * _.mixin({ 'capitalize': capitalize });
    * _.capitalize('fred');
    * // => 'Fred'
    *
    * _('fred').capitalize().value();
    * // => 'Fred'
+   *
+   * _.mixin({ 'capitalize': capitalize }, { 'chain': false });
+   * _('fred').capitalize();
+   * // => 'Fred'
    */
   function mixin(object) {
     forEach(functions(object), function(methodName) {