Release 0.15.3

# History

## 0.15.3

Install/update via the bootstrap script:

```shell
wget https://raw.githubusercontent.com/dokku/dokku/v0.15.3/bootstrap.sh
sudo DOKKU_TAG=v0.15.3 bash bootstrap.sh
```

### New Features

- #3489: @josegonzalez feat: upgrade herokuish to 0.5.0 (Ubuntu 18.04)

contrib/dokku-installer.py

@@ -10,7 +10,7 @@ import subprocess
 import sys
 import threading
 
-VERSION = 'v0.15.2'
+VERSION = 'v0.15.3'
 
 hostname = ''
 try: