Remove database credentials

Try this... Locally:

```
export ROOTCAUSE_DB_USER=...
export ROOTCAUSE_DB_PASSWORD=...
export ROOTCAUSE_DB_HOST=...
export ROOTCAUSE_DB_NAME=...
```

On Heroku:

```
heroku config:set ROOTCAUSE_DB_USER=...
heroku config:set ROOTCAUSE_DB_PASSWORD=...
heroku config:set ROOTCAUSE_DB_HOST=...
heroku config:set ROOTCAUSE_DB_NAME=...
```