Just Change in build.gradle file
classpath 'com.android.tools.build:gradle:1.3.0'
To
classpath 'com.android.tools.build:gradle:2.0.0'
Now GoTo
-> menu choose File
-> Invalidate Caches/Restart
...
Choose first option: Invalidate and Restart
Android Studio would restart.
After this, it should work normally.