Pin expect.js to 0.2

As long as Automattic/expect.js#102 isn't resolved, 0.3 causes bugs.

Author: fb55

package.json

@@ -27,7 +27,7 @@
   },
   "devDependencies": {
     "mocha": "*",
-    "expect.js": "*",
+    "expect.js": "0.2",
     "jshint": "~2.3.0",
     "benchmark": "~1.0.0",
     "jsdom": "~0.8.9"