title: sbt native packager doesn't create scripts under target/universal/stage/bin
body: <p>I'm trying to use JavaAppPackaging from sbt-native-packager. My understanding is, that when I run:</p>
  
  <p><code>sbt stage</code></p>
  
  <p>I should get a directory target/universal/stage/bin with some startup scripts. Now I only get lib which contains my jar and it's dependencies. </p>
  
  <p>Here's the relevant parts of my build.sbt:</p>
  
  <pre><code>val scalatra = "org.scalatra" %% "scalatra" % "2.3.1"
  
  enablePlugins(JavaAppPackaging)
  
  lazy val root = (project in file(".")).
    settings(
      name := "myapp",
      version := "0.2",
      scalaVersion := "2.11.6",
      libraryDependencies += scalatra
    )
  </code></pre>
  
  <p>Also, my plugins.sbt has this:</p>
  
  <pre><code>addSbtPlugin("com.typesafe.sbt" % "sbt-native-packager" % "1.0.0")
  </code></pre>
  
  <p>I'm using sbt 0.13.8.</p>
  
  <p>So why don't I get the startup scripts, what am I missing?</p>