Allow array values in options

This is needed for example for the 'except' option to allow multiple exceptions.

Now you can use multiple exceptions like this:
```javascript
groc: {
	all: {
		src: ["src/**/*.js"],
		options: {
			out: "doc/",
			except: [
				"**/all.js",
				"**/*.min.js",
				"**/*-min.js"
			]
		}
	}
}
```