Missing RR implementation & advanced usage

* Added support for MX, TXT, PTR, SOA, ANY, NS, AAAA records
* Added additional & authority message parsers & dumper (includes RobinvdVleuten's https://github.com/reactphp/react/pull/272)
* Fixed TCP retry parser & dumper. In TCP first two octets describe the length of data
* Added explain method to Message, Query, Record for detailed information in a dig like format.
* Added examples
* Message->questions now stores array of Query objects instead of array of array
This logic needs to be moved elsewhere. Not sure yet where, but "value objects" really should not contain such a dependency on the environment.