update travis CI config

Author: petekanev

.travis.yml

@@ -16,6 +16,8 @@ android:
   - tools
   - build-tools-23.0.3
   - android-23
+  - extra-android-support
+  - extra-android-m2repository
   - sys-img-armeabi-v7a-android-21
 before_cache:
   - rm -f $HOME/.gradle/caches/modules-2/modules-2.lock