Gruntfile addition for jsdoc-amddcl.

Grunt config for jsdoc-amddcl. To use it:

```shellsession
> npm install
> grunt jsdoc-amddcl
```

The documents as well as exported doclets will be found in “out” directory.

To use syntax highlighting, you’ll need to manually install prettify, following the instruction [here](https://github.com/ibm-js/jsdoc-amddcl/#setup).

Also, `npm update` does not seem to grab updates in git://github.com/ibm-js/jsdoc-amddcl.git#master. You can do below to grab updates:

```shellshession
> rm -Rf node_modules/jsdoc-amddcl
> npm install git://github.com/ibm-js/jsdoc-amddcl.git
```