title: proguard + crashlytics crash
body: <p>I have integrated Crashlytics in my project, Now when I enable proguard, App Crashes. Have tried to exclude all the classes from crashlytics with no success</p>
  
  <p>File proguard-rules.pro file has the following</p>
  
  <pre><code>-keep class io.fabric.sdk.android.** { *; }
  -keep interface io.fabric.sdk.android.** { *; }
  -keep class com.digits.sdk.android.core.** { *; }
  -keep interface com.digits.sdk.android.core.** { *; }
  -keep class com.twitter.sdk.android.** { *; }
  -keep interface com.twitter.sdk.android.** { *; }
  
  -keep class io.fabric.** { *; }
  -keep interface io.fabric.** { *; }
  -keep class com.digits.** { *; }
  -keep interface com.digits.** { *; }
  -keep class com.twitter.** { *; }
  -keep interface com.twitter.** { *; }
  -keep class com.crashlytics.** { *; }
  -keep interface com.crashlytics.** { *; }
  -keep class com.crashlytics.** { *; }
  -dontwarn com.crashlytics.**
  </code></pre>
  
  <p>I am getting an error as</p>
  
  <pre><code>com.example.app E/Answers: Failed to submit events task
      java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask@1d060ef0 rejected from java.util.concurrent.ScheduledThreadPoolExecutor@31c1ac69[Shutting down, pool size = 1, active threads = 0, queued tasks = 1, completed tasks = 9]
          at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2011)
          at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:793)
          at java.util.concurrent.ScheduledThreadPoolExecutor.delayedExecute(ScheduledThreadPoolExecutor.java:298)
          at java.util.concurrent.ScheduledThreadPoolExecutor.schedule(ScheduledThreadPoolExecutor.java:503)
          at java.util.concurrent.ScheduledThreadPoolExecutor.submit(ScheduledThreadPoolExecutor.java:602)
          at java.util.concurrent.Executors$DelegatedExecutorService.submit(Executors.java:593)
          at com.crashlytics.android.answers.AnswersEventsHandler.executeAsync(Unknown Source)
          at com.crashlytics.android.answers.AnswersEventsHandler.processEvent(Unknown Source)
  </code></pre>
  
  <p>I have also looked at crashlytics document and tried every possible combinations.
  can someone please guide me on this</p>