chore(build): upgrade build tools in ci config

Author: simpleton

.travis.yml

@@ -11,8 +11,8 @@ android:
     - tools
     - tools # see https://github.com/travis-ci/travis-ci/issues/6040#issuecomment-219367943
     - platform-tools
-    - build-tools-26.0.2
-    - android-26
+    - build-tools-28.0.3
+    - android-28
     - extra-android-m2repository
 
 script: ./gradlew clean check test

app/build.gradle

@@ -29,7 +29,7 @@ dependencies {
 }
 
 android {
-    compileSdkVersion 26
+    compileSdkVersion 28
     buildToolsVersion '28.0.3'
 
     signingConfigs {