include a section on how the compiler team functions

[nikomatsakis]

We should talk about how the compiler team itself functions:

• Chatting typically in #rustc on IRC
• Open-to-public triage meetings in #rustc on IRC at 10am Boston time on Thursday
  • Careful around US daylight savings time :/
• How to find open issues
• Mentoring and how to ask for it (Writing mentored issues #64)