Make grunt tasks check for dependencies

[shaoshing]

npm install is required

This PR uses the grunt-check-dependencies package to add the ability to check for package dependencies before running some grunt tasks, and will inform you when npm install is needed. Below are the tasks that will check dependencies:

• grunt test (npm test)
• grunt compile
• grunt debug
• when running grunt debug, it will keep monitoring the package.json file for change of dependencies.

[baaygun]

Is this going to work offline? It would suck to block the build progress if there are errors with package checking, can you make it warn only instead?

[shaoshing]

@volfied that's a good question. The package itself does not support silenced warning, but you can use the --force option to ask Grunt to ignore the warnings. Given that we rarely work without internet, I think this is a good enough workaround? Please let me know your thoughts.

[baaygun]

Alright, I'm semi-convinced this helps. We'll see how it goes!