fix: travis build

- Do not longer build with node@6
- Use build-tools-27.03
- Use Api23 emulator

Author: dtopuzov

Diff for: .travis.yml

@@ -1,10 +1,9 @@
 env:
   global:
-    - NODE_VERSION=6
     - NODE_VERSION=8
-    - EMULATOR_API_LEVEL=22
+    - EMULATOR_API_LEVEL=23
     - ANDROID_VERSION=25
-    - ANDROID_BUILD_TOOLS_VERSION=26.0.2
+    - ANDROID_BUILD_TOOLS_VERSION=27.0.3
     - ANDROID_ABI=armeabi-v7a
     - APPIUM_VERSION=1.7.0
     - EMULATOR_NAME=test
@@ -23,24 +22,6 @@ matrix:
         - npm run tslint
     - stage: "Build"
       os: osx
-      env:
-        - Build="iOS"
-      osx_image: xcode9.3
-      language: node_js
-      node_js: "6"
-      jdk: oraclejdk8
-      before_install: 
-        - cd nativescript-angular
-        - npm install
-        - cd ../tests
-        - npm install
-        - cd ..
-      script: 
-        - cd nativescript-angular
-        - npm run ngc
-        - cd ../tests
-        - tns build ios
-    - os: osx
       env:
         - Build="iOS"
       osx_image: xcode9.3
@@ -58,28 +39,6 @@ matrix:
         - npm run ngc
         - cd ../tests
         - tns build ios
-    - language: android
-      node_js: "6"
-      os: linux
-      env:
-        - Build="Android"
-      jdk: oraclejdk8
-      before_install: 
-        - echo no | android create avd --force -n $EMULATOR_NAME -t "android-"$EMULATOR_API_LEVEL --abi $ANDROID_ABI --tag $ANDROID_TAG -c 12M
-        - QEMU_AUDIO_DRV=none emulator -avd $EMULATOR_NAME -no-window &
-        - nvm install $NODE_VERSION
-        - cd nativescript-angular
-        - npm install
-        - cd ../tests
-        - npm install
-        - cd ..
-        - android-wait-for-emulator
-        - adb shell input keyevent 82 &
-      script: 
-        - cd nativescript-angular
-        - npm run ngc
-        - cd ../tests
-        - tns build android
     - language: android
       node_js: "8"
       os: linux
@@ -107,20 +66,13 @@ android:
   components:
     - tools
     - platform-tools
-    - build-tools-25.0.2
     - build-tools-$ANDROID_BUILD_TOOLS_VERSION
-    - android-25
     - android-$EMULATOR_API_LEVEL
     - extra-google-google_play_services
     - extra-google-m2repository
     - extra-android-m2repository
-    - addon-google_apis-google-25
     # Specify at least one system image,
     # if you need to run emulator(s) during your tests
-    - sys-img-armeabi-v7a-android-26
-    - sys-img-armeabi-v7a-android-25
-    - sys-img-armeabi-v7a-android-17
-    - sys-img-armeabi-v7a-android-19
     - sys-img-armeabi-v7a-google_apis-$EMULATOR_API_LEVEL
   licenses:
     - ".+"