Error:Execution failed for task ':app:packageRelease'.
Unable to compute hash of /Users/koshousakai/Desktop/runningdemo/RunningTwo/app/build/intermediates/classes-proguard/release/classes.jar
proguard-rules.pro没配置好，具体配置方法参考这两篇博客。
http://blog.csdn.net/banana1006034246/article/details/46985519
http://blog.csdn.net/lovexjyong/article/details/24652085