Fix Travis for Android API 27

Roger Hu · Roger Hu · commit 182cc12a4311 · 2018-01-13T09:57:46.000-08:00
diff --git a/.travis.yml b/.travis.yml
@@ -19,6 +19,7 @@ android:
 
 before_install:
     - pip install --user codecov
+    - yes | sdkmanager "platforms;android-27"
 
 script:
   - ./gradlew clean testDebugUnitTest jacocoTestReport
