A clean up of some recent activity regarding dependencies. See https://github.com/Modernizr/Modernizr/pull/1159

These dependencies are only used for testing. They should be moved to devDependencies.

The benefits for this include a faster install time, and suppressing the `>> Local Npm module "grunt-contrib-qunit" not found` errors references in Issue #1154

Removing qunit from the default task, since it is now a conditional dev dependency.