Ever more informative, explicit, and complete release checklist.

[jmchilton]

• Update announcement activities to reflect release notes handled by devs in a diffrent, earlier step.
• Add example post links for various announcement activities.
• Add credential location information for Twitter.
• Add branch-time item to update bioblend target testing.
• Update issue to describe testing update more accurately (my previous assumptions did not match our actual practice).
• Add item for scheduling a committer priority meeting (as done for this release by @martenson - thanks for taking charge on that!).

[martenson]

awesome @jmchilton !