title: Set different minSdkVersion for testAndroid than for main app
body: <p>Is it possible to set a different <code>minSdkVersion</code> for tests than for the app itself? I ask because I want to use the new Test Support Library and UI Automator for testing. However, this is only available on API 18+. At the same time, I still want to support older versions of Android, albeit not as thoroughly tested. What do I need to add to my <code>build.gradle</code> file in order to do this?</p>
  
  <p>To clarify, I am using Android Studio and the "new" Gradle-based project structure.</p>