Change SDK version travis

Author: bhavik66

.travis.yml

@@ -16,7 +16,7 @@ android:
     - platform-tools
     - tools
     - build-tools-28.0.2
-    - android-28
+    - android-27
     - extra-android-m2repository
     - extra-google-google_play_services
     - extra-google-m2repository