Adding bugs url and updating devDependencies

Added 'bugs' URL to make the package.json validator a bit happier: http://package-json-validator.com/

Tweaked the 'description' slightly.

Updating devDependencies for Mocha and Chai.
> **Outdated Dev Dependencies**
> - mocha (package: 1.8.x, latest: 1.18.2)
> - chai (package: 1.5.x, latest: 1.9.1)
Merge pull request #1 from pdehaan/patch-1

Adding bugs url and updating devDependencies