Automate release steps

[glasserc]

Per #345 (comment), it's often better for release steps to be automated than documented. A good platform for the automation of release steps might be zest.releaser and its hooks.

[peterbe]

Ethan documented the release/deploy steps and in this PR and turned those documented steps into a Python script.

The full deploy process still contains some manual steps. I.e. the bin/deployment-bug.py just helps you get a link to file a bug for OPs.

With that in mind I'm going to boldly close this issue for now.