Use Oracle JDK instead of Open JDK

We can follow these instructions: https://www.digitalocean.com/community/tutorials/how-to-install-java-with-apt-get-on-ubuntu-16-04

```
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java8-installer
```

Further reading: https://github.com/CellProfiler/CellProfiler/issues/2798

This should be done before #10.