Add unit tests

- add APK file containing a simple app that tries to use coroutines every 2 seconds, and would fail with earlier versions of APKTool
- add unit test for decoding the app
- add unit test for building a decoded app

brut.apktool/apktool-lib/src/main/java/brut/androlib/Androlib.java

@@ -757,7 +757,6 @@ public class Androlib {
         return ! stored.exists() || BrutIO.recursiveModifiedTime(working) > BrutIO .recursiveModifiedTime(stored);
     }
 
-
     private boolean isFile(File working) {
         return working.exists();
     }