CHANGELOG.md in sk_api_schema-0.9.1 vs CHANGELOG.md in sk_api_schema-0.9.2

@@ -3,9 +3,11 @@
 See [commit messages](https://github.com/salesking/sk_api_schema/commits/) for details.
 Also sign up to our [Developer Newsletter](http://www.salesking.eu/dev/newsletter/) to stay up-to-date !!!
 
 ##2014-01
 
+* line_item price_single is required,
+* line item empty tax,discount now return null instead of 0
 * filter documents by products (product_ids)
 
 ##2013-12
 
 * add cost_total, gross_margin to documents