Compiling with Java 1.8

Gives the classical "your Scala is too old" error:

```
[ERROR] error: error while loading CharSequence, class file '...CharSequence.class)' is broken
[INFO] (class java.lang.RuntimeException/bad constant pool tag 18 at byte 10)
```

Which is easy to fix: Update the Scala dependency in the `pom.xml` to at least 2.10.3+ and Goose compiles with Java 1.8.
