Add missing changes.txt for ruflin#670

Author: krzaczek

changes.txt

@@ -2,6 +2,8 @@ CHANGES
 
 2014-08-25
  - Top-level filter parameter in search has been renamed to post_filter #669 #670
+ - Deprecated: Elastica\Query::setFilter() is deprecated. Use Elastica\Query::setPostFilter() instead. #669
+ - Deprecated: Elastica\Query::setPostFilter() passing filter as array is deprecated. Pass instance of AbstractFilter instead. #669
 
 2014-08-22
  - Fixed escaping of / character in Elastica\Util::escapeTerm(), removed usage of JSON_UNESCAPED_SLASHES in Elastica\JSON #660