Remove trailing commas for IE 9 compatibility

Summary: IE 9 doesn't like trailing commas. When we introduced eslint, we added
a bunch of trailing commas, which makes IE 9 sad.

Test Plan:
 - `make lint`
 - Visit http://localhost:7936/ using IE 9 on browserstack.
 - See that the math loads, and there are no errors in the F12 developer tools.

@kevinb

package.json

@@ -17,7 +17,7 @@
   "devDependencies": {
     "browserify": "^10.2.4",
     "clean-css": "~2.2.15",
-    "eslint": "^1.10.2",
+    "eslint": "^1.10.3",
     "express": "~3.3.3",
     "glob": "^5.0.15",
     "jasmine": "^2.3.2",