Fixed #148 Server builds don't work in FF (or Safari?)

Also fixed the warning introduced by 7948856e34c6f984ed656b35ac7284bae7f55d4b:
```>> Local Npm module "grunt-contrib-qunit" not found. Is it installed?```
Merge pull request #150 from markcarver/mozilla_addon_sdk_fix

Fixed #148 Server builds don't work in FF (or Safari?)