Support MongoDB "Dot Notation" for arrays and subdocuments

The MongoDB [Dot Notation](http://docs.mongodb.org/manual/core/document/#dot-notation) allows querying subdocuments and arrays.

**Example for subdocuments**

The document:
```javascript
var doc = 
{ magic: 
   { kittens: 'lazers',
     unicorns: 'sparkles',
     monkeys: { voodoo_score: 400, apples: 300 } },
  blackmagic: 'yes' };
```

The query:
```javascript
var query = {
  'magic.monkeys.voodoo_score' : { '$gt' : 300 }
};
```

The magic:
```javascript
var match = qry(query);
console.log('The assumption that monkeys have great Voodoo score is', match(doc)); 

// The assumption that monkeys have great Voodoo score is true
```