I am not sure what this error means.
Execution failed for task \':excelSior:packageAllDebugClassesForMultiDex\'.
> java.util.zip.ZipException: duplicate
check your dependencies versions, you must have compatible versions put attention specially to com.google packages, must have same version like:
compile 'com.google.android.gms:play-services:8.3.0'
compile 'com.google.android.gms:play-services-maps:8.3.0'
Both are 8.3.0, if you have another version compilation will throw that exception.