Update actionpack/CHANGELOG.md

actionpack/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   `respond_to` and `respond_with` now raise ActionController::UnknownFormat instead
+    of directly returning head 406. The exception is rescued and converted to 406
+    in the exception handling middleware. *Steven Soroka*
+
 *   Allows `assert_redirected_to` to match against a regular expression. *Andy Lindeman*
 
 *   Add backtrace to development routing error page. *Richard Schneeman*
@@ -12,7 +16,7 @@
 *   Make current object and counter (when it applies) variables accessible when
     rendering templates with :object / :collection. *Carlos Antonio da Silva*
 
-*   JSONP now uses mimetype application/javascript instead of application/json *omjokine*
+*   JSONP now uses mimetype application/javascript instead of application/json. *omjokine*
 
 *   Allow to lazy load `default_form_builder` by passing a `String` instead of a constant. *Piotr Sarnacki*