Feature: Add TcpTransportExecutor to send DNS queries over TCP/IP connection, add SelectiveTransportExecutor to retry with TCP if UDP is truncated and automatically select transport protocol when no explicit udp:// or tcp:// scheme is given in Factory. (#145, #146, #147 and #148 by @clue)

Feature: Support escaping literal dots and special characters in domain names. (#144 by @clue)