update changelog w/ row_classes addition

CHANGELOG.md

@@ -6,6 +6,7 @@ All notable changes to this project will be documented in this file.
 ### Enhancements
 
 * Use the more appropriate `add_meta_boxes` hook for adding metaboxes to post-edit screen. Thanks [@inspiraaz](https://github.com/inspiraaz) for reporting. ([#161](https://github.com/WebDevStudios/CMB2/issues/161))
+* Add a `row_classes` field param which allows you to add additional classes to the cmb-row wrap. This parameter can take a string, or array, or can take a callback that returns a string or array. The callback will receive `$field_args` as the first argument, and the CMB2_Field `$field` object as the second argument. Reported/requested in [#68](https://github.com/WebDevStudios/CMB2/issues/68).
 
 ## 2.0.1 - 2015-02-02