Suggestions on the build steps in the README

[jkomg]

Comments from Lightbend Reviewers

• [ ] sbt-native-packager used in this example is old, so it suffers from the duplicate layer bug
• [x] DS_STORE is in version control, it shouldn't be.
• [ ] Various akka.io.dns settings in build.sbt are for a library that isn't included in this application and therefore not relevant; these settings should be removed

[szihai]

Can I get the updated version of the build file?

[stevemar]

I randomly created #9 -- it should address the second issue in your list