Update .travis.yml

Author: lini

.travis.yml

@@ -29,15 +29,15 @@ matrix:
     - language: android
       os: linux
       env:
-        - WebpackAndroid="26"
+        - WebpackAndroid="28"
       jdk: oraclejdk8
       before_install: nvm install 8
       script:
         - cd src && npm run build && cd ../demo && npm i && tns build android --env.uglify --env.snapshot
         - cd ../demo-angular && npm i && tns build android --env.uglify --env.snapshot --env.aot
     - language: android
       env: 
-        - BuildAndroid="26"
+        - BuildAndroid="28"
       os: linux
       jdk: oraclejdk8
       before_install: nvm install 8.11.4
@@ -80,9 +80,8 @@ android:
   components:
     - tools
     - platform-tools
-    - build-tools-27.0.3
-    - android-26
-    - android-23
+    - build-tools-28.0.2
+    - android-28
     - extra-android-m2repository
 
 before_install: