Added: Request, Response, DnsClient classes; DnsClient::getDomainRecords method.
Added: addRecord methods.
Refactoring: replace all addTypeRecord methods by one universal method for all types.
Added: method editRecord, method deleteRecord; constants TYPE_, constants FIELD_.
Added methods match, matchRecords, editRecords, deleteRecords (modification and deletion of records by any field)
Added: first tests for Response class.
Added: some tests for Response class.
Changed test preferences.