Use cucumber-jvm 1.1.6-SNAPSHOT, which fixes a bug with stepdefs.json

Cucumber-JVM 1.1.5 would only write out `stepdefs.json` if you were using the command-line runner (`cucumber.api.cli.Main`), but not if you were using the JUnit runner (which you're using).

This bug was fixed in cucumber/cucumber-jvm#3e4dae2c35f99d424f7a1a5f447ba36aced51aa1, which is currently in cucumber-jvm 1.1.6-SNAPSHOT.

We plan on releasing 1.1.6 in a week or two, but it should be ok to use the snapshot in the interim.