message: Add details to release instructions
diff: @@ -59,7 +59,10 @@ need to be done at every release.
  gpg --gen-key
  # Checkout ASF dist repo
  - svn checkout https://dist.apache.org/repos/dist/dev/incubator/superset/ ~/svn/superset
  +
  + svn checkout https://dist.apache.org/repos/dist/dev/incubator/superset/ ~/svn/superset_dev
  +
  + svn checkout https://dist.apache.org/repos/dist/incubator/superset/ ~/svn/superset
  cd ~/svn/superset
  @@ -95,15 +98,27 @@ Now let's craft a source release
  scripts/sign.sh apache-superset-${VERSION}-source.tar.gz
  ```
  -Now let's ship this into svn
  +Now let's ship this RC into svn's dev folder
  ```bash
  # cp or mv the files over to the svn repo
  - mkdir ~/svn/superset/${VERSION}/
  + mkdir ~/svn/superset_dev/${VERSION}/
  cp apache-superset-${VERSION}* ~/svn/superset/${VERSION}/
  cd ~/svn/superset/
  svn add ${VERSION}
  svn commit
  ```
  -Now you're ready to announce the release on the mailing list
  +Now you're ready to start the VOTE thread.
  +
  +Upon a successful vote, you'll have to copy the folder into the non-"dev/"
  +folder.
  +```bash
  + cp -r ~/svn/superset_dev/${VERSION}/ ~/svn/superset/${VERSION}/
  + cd ~/svn/superset/
  + svn add ${VERSION}
  + svn commit
  +```
  +
  +Now you can announce the release on the mailing list, make sure to use the
  +proper template
  