[addons] Renamed update() directives to commands

docs/09.6-update.md

@@ -51,9 +51,9 @@ var newData = React.addons.update(myData, {
 
 While the syntax takes a little getting used to (though it's inspired by [MongoDB's query language](http://docs.mongodb.org/manual/core/crud-introduction/#query)) there's no redundancy, it's statically analyzable and it's not much more typing than the mutative version.
 
-The `$`-prefixed keys are called *directives*. The data structure they are "mutating" is called the *target*.
+The `$`-prefixed keys are called *commands*. The data structure they are "mutating" is called the *target*.
 
-## Available directives
+## Available commands
 
   * `{$push: array}` `push()` all the items in `array` on the target
   * `{$unshift: array}` `unshift()` all the items in `array` on the target