Try to apply Groovy support to vendingmachine fork

[keilw]

Since the forked demo https://github.com/JavaMoney/vendingmachine is also based on Groovy/Gradle and Spock, it would be great to integrate with Groovy support where applicable.

[msgilligan]

Actually, vendingmachine is written in Java, with JUnit tests in Java and Groovy. Gradle is used for the build and Spock is listed in the Gradle file as a dependency, but I don't see any Spock tests. But certainly the project could be made even more Groovy!

Before we can start using "groovy-money" in other projects, we'll need to publish it as a jar file. I'll open an issue for that task.

Update: It's Issue #13.