Call Resolver.query instead of Object.send

Fixes issue with demo code:

```
(greg.poirier@oppie)(~/dev/ext/net-dns)(master)
bundle exec demo/check_soa.rb google.com
nspr002.va.opower.it. (10.20.48.51): demo/check_soa.rb:71:in `block (2 levels) in <main>': undefined method `google.com' for #<Net::DNS::Resolver:0x007fcba232f648> (NoMethodError)
```