Fixed: format multilevel json to querystring correctly

Consider follow json convert to http query string
```json
{
    "$or": [
        {
            "username": {
                "$regex": "admin"
            },
            "name": {
                "$regex": "admin"
            }
        }
    ], 
    "limit": 10, 
    "page": 1, 
    "status": {
        "$ne": "removed"
    }
}

```

TO Query String
```
GET /users?status%5B$ne%5D=removed&$or%5B0%5D%5Busername%5D%5B$regex%5D=ad&$or%5B1%5D%5Bname%5D%5B$regex%5D=admin
```

So, we can query mongo directly from angular.js