Added capability to validate arrays directly against a schema

The current implementation lacks the ability to validate against a schema. That is, a schema such as the following always returns as valid regardless: 

```javascript
var s = {
  type: 'array'
}
```

This is not desired when actually wishing to validate the contents of an array (such as a grid), thus shoehorning the user into wrapping their grid in an object. This PR adds a secondary logical path that is available if the schema's type is 'array'.