JSON.strigify on non string objects

non string objects are easily converted to strings.
this is cool if you have json or jsonb data column


quick esample:  
```javascript
    db.insert( 'pages',
		[
			'url',
			'title',
			'components',                    // jsonb column
			'created_at',
			'updated_at'
		],
		[
			'/',
			'Home Page',
			['a','custom','array'],         // previously it had to be JSON.stringify(['a','custom','array'])
			'now()',
			'now()'
		],
		callback
    );
```