Update IRC clients sections

- Remove recommendation for a specific IRC client (irssi)

- Remove example usage of irssi (different clients work differently)

- Remove alias tip (not common enough in all clients to be useful)

- Add tip about smart filters existing in some clients
Update Google+ Hangouts sections

- Remove mention of Andrew leading the hangouts
  - Statement has been untrue for a while
  - We now want students to take initiative and lead meetings

- Add step for providing us with a Google+ email address
  - Unfortunately G+ is required for hangouts, although a limited
    1-on-1 hangout is possible through Gmail without a G+ profile