title: proguard issue in Gradle
body: <p>I am trying build my APP I am getting the following error: All this time App used to generate the build properly. </p>
  
  <p>After I upgraded my compileSdkVersion and build to 23, GMS to 8.1, AsyncHttpclient to 1.4.9. I am getting the following error.</p>
  
  <p>Not sure what to do:  </p>
  
  <pre><code>  Warning:com.google.android.gms.internal.zzac: can't find referenced class android.net.http.AndroidHttpClient
      Warning:com.google.android.gms.internal.zzw: can't find referenced method 'void addHeader(java.lang.String,java.lang.String)' in program class com.google.android.gms.internal.zzw$zza
      Warning:com.google.android.gms.internal.zzw$zza: can't find referenced method 'void setURI(java.net.URI)' in program class com.google.android.gms.internal.zzw$zza
      Warning:there were 2 unresolved references to classes or interfaces.
               You may need to add missing library jars or update their versions.
               If your code works fine without the missing classes, you can suppress
               the warnings with '-dontwarn' options.
               (http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedclass)
      Warning:there were 2 unresolved references to program class members.
               Your input classes appear to be inconsistent.
               You may need to recompile the code.
               (http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedprogramclassmember)
      :app:proguardRelease FAILED
      Error:Execution failed for task ':app:proguardRelease'.
      &gt; java.io.IOException: Please correct the above warnings first.
  </code></pre>
  
  <p>What could be wrong here?</p>