Merge pull request #1 from sbp/master

Merge with upstream
Make core.py more cross-IRCd compatible on connection: 1) Only send JOIN and WHO commands when RPL_WELCOME (001) is received from the server. 2) When responding to a PING, the PONG argument is the same as the received PING argument.
Merge pull request #41 from musalbas/master

Make the connection step more IRCd cross-compatible