Fix recommended npm hook

Author: joliss

README.md

@@ -44,13 +44,13 @@ Next, run
 In this example, it will create `test/multidep` and install broccoli 0.16.3
 and broccoli 1.0.0 somewhere inside the `test/multidep` directory.
 
-To run `multidep` automatically after `npm install`, add it as a "postinstall"
+To run `multidep` automatically after `npm install`, add it as a "pretest"
 hook to your `package.json`:
 
 ```json
 {
   "scripts": {
-    "postinstall": "multidep test/multidep.json",
+    "pretest": "multidep test/multidep.json",
     "test": "..."
   }
 }