Add release channel automation

[brson]

Before 1.0 we want to change the release process to have multiple parallel release channels ('nightly', 'beta', 'stable', probably). This will require a bunch of new automation.

[brson]

The automation for distribution is done, but for integration is not.

[aturon]

Nominating for beta milestone.

[pnkfelix]

assigning 1.0-beta. (We could struggle on without it, but it makes more sense to get it deployed by that time).