title: ionic facebook and barcodescanner issue
body: <p>I have a problem with facebook plugin and barcode scanner, first i created a projects separate to check how facebook plugin work and was working perfect, but when I added the facebook plugin to my project where im using barcodescanner plugin i cant run the project in android, I got the following exception:</p>
  
  <pre><code> BUILD FAILED
  
  Total time: 10.111 secs
  FAILURE: Build failed with an exception.
  
  * What went wrong:
  Execution failed for task ':transformClassesWithJarMergingForDebug'.
  &gt; com.android.build.api.transform.TransformException: java.util.zip.ZipException: duplicate entry: com/google/zxing/BarcodeFormat.class
  
  * Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
  Error: cmd: Command failed with exit code 1 Error output:
  Note: Some input files use or override a deprecated API.
  Note: Recompile with -Xlint:deprecation for details.
  
  FAILURE: Build failed with an exception.
  
  * What went wrong:
  Execution failed for task ':transformClassesWithJarMergingForDebug'.
  &gt; com.android.build.api.transform.TransformException: java.util.zip.ZipException: duplicate entry: com/google/zxing/BarcodeFormat.class
  
  * Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
  
  [ERROR] An error occurred while running cordova run android (exit code 1).
  </code></pre>