Heads up: branching branch-3.0.0-beta1 off of branch-3.0

[Andrew Wang]

Hi folks,

We've driven the blocker count down to 0, and I went through and made sure
the fix versions and release notes and so on are all lined up.

I'm going to cut branch-3.0.0-beta1 off branch-3.0 and try and get RC0 out
today.

Cheers,
Andrew