Updated travisCI to Android API 29

Author: jkasten2

.travis.yml

@@ -10,14 +10,14 @@ android:
             # https://github.com/travis-ci/travis-ci/issues/6193
             # Required to get the newest platform-tools.
     - platform-tools
-    - build-tools-28.0.3
-    - android-28
+    - build-tools-29.0.3
+    - android-29
   licenses:
     - '.+'
     - 'android-sdk-license-.+'
 before_install:
-    - yes | sdkmanager "platforms;android-28"
-    - yes | sdkmanager "build-tools;28.0.3"
+    - yes | sdkmanager "platforms;android-29"
+    - yes | sdkmanager "build-tools;29.0.3"
     - pwd
     - ls -la
     - cd OneSignalSDK