title: .gitignore does not ignore one folder
body: <p>I've got the following in my .gitignore:</p>
  
  <pre><code>#built application files
  *.apk
  *.ap_
  # files for the dex VM
  *.dex
  # Java class files
  *.class
  # generated files
  bin/
  gen/
  # Local configuration file (sdk path, etc)
  local.properties
  # Windows thumbnail db
  Thumbs.db
  # OSX files
  .DS_Store
  # Eclipse project files
  .classpath
  .project
  # Android Studio
  .idea
  build/
  cache.properties.lock
  .idea/workspace.xml
  *.iws
  .gradle/
  **/.gradle/
  </code></pre>
  
  <p>However, whenever I make changes to my app, git includes files like <code>.gradle/1.12/taskArtifacts/cache.properties.lock</code> to the commit.</p>
  
  <p>What's wrong here? Why does it work with the folder <code>build/</code> but not with <code>.gradle/</code>?</p>