Release 0.18.4

# History

## 0.18.4

Install/update via the bootstrap script:

```shell
wget https://raw.githubusercontent.com/dokku/dokku/v0.18.4/bootstrap.sh
sudo DOKKU_TAG=v0.18.4 bash bootstrap.sh
```

### Other

- #3703: @scjody Update DOKKU_SCALE from Procfile during ps:scale

contrib/dokku-installer.py

@@ -10,7 +10,7 @@ import subprocess
 import sys
 import threading
 
-VERSION = 'v0.18.3'
+VERSION = 'v0.18.4'
 
 hostname = ''
 try: