Add releases and release checklist docs

[david415]

please review. note that i cut a v0.0.1 release as of today. pretty sure i did it correctly but feel free to make changes or whatever.

[david415]

ah notice the entry for minclient in Gopkg.lock:

[[projects]]
  branch = "master"
  name = "github.com/katzenpost/minclient"
  packages = [
    ".",
    "block"
  ]
  revision = "b1f54e28d320fb6e4ef0746839fe87ebdc944ff7"

it's not specifying the tag. this is in contrast to the entry for core which does specify the tag:

[[projects]]
  name = "github.com/katzenpost/core"
  packages = [
    "constants",
    "crypto/ecdh",
    "crypto/eddsa",
    "crypto/rand",
    "epochtime",
    "log",
    "monotime",
    "pki",
    "queue",
    "sphinx",
    "sphinx/commands",
    "sphinx/constants",
    "sphinx/internal/crypto",
    "sphinx/path",
    "thwack",
    "utils",
    "wire",
    "wire/commands",
    "worker"
  ]
  revision = "50a328944dc7dc026b7066237b391de87ad916a8"
  version = "v0.0.1"

we should try to fix this so that we can release stuff that is older than HEAD of master.