Support load-grunt-tasks in a smarter way.

[mirek]

Reported by @azder:

Also, the same thing with:

    "load-grunt-config":       "^0.8.0-beta.1",
    "load-grunt-tasks":        "^0.6.0",

I'm using both for loading Grunt related packages, and yet, the report is:

    npm uninstall --save-dev grunt
    npm uninstall --save-dev grunt-bump
    npm uninstall --save-dev grunt-concurrent
    npm uninstall --save-dev grunt-contrib-clean
    npm uninstall --save-dev grunt-contrib-concat
    npm uninstall --save-dev grunt-contrib-jshint
    npm uninstall --save-dev grunt-contrib-requirejs
    npm uninstall --save-dev grunt-contrib-watch
    npm uninstall --save-dev grunt-nodemon
    npm uninstall --save-dev grunt-replace