Updates to run with Ratpack enabled buildpack

This change updates the manifest of the project to run with the
Ratpack enabled buildpack located at https://github.com/nebhale/java-
buildpack-with-ratpack.  It depends on the distZip artifact created as
part of the build so the following should now work (albeit slowly):

./gradlew distZip
cf push
Merge pull request #1 from nebhale/ratpack-buildpack

Updates to run with Ratpack enabled buildpack
Thanks Ben for the help!