Start using Travis in preparation for auto-release building.

.travis.yml

+# http://docs.travis-ci.com/user/languages/android/
+language: android
+jdk: oraclejdk8
+sudo: false
+
+before_cache:
+  - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
+  - rm -fr $HOME/.gradle/caches/*/plugin-resolution/
+
+cache:
+  directories:
+    - $HOME/.gradle/caches/
+    - $HOME/.gradle/wrapper/
+    - $HOME/.android/build-cache
+
+env:
+  global:
+    - MIN_SDK_VERSION=14
+    - COMPILE_SDK_VERSION=25
+    - ANDROID_BUILD_TOOLS=25.0.2
+    - ADB_INSTALL_TIMEOUT=5 # minutes
+
+android:
+  components:
+    - tools
+    - platform-tools
+    - tools
+    - build-tools-$ANDROID_BUILD_TOOLS
+    - android-$MIN_SDK_VERSION
+    - android-$COMPILE_SDK_VERSION
+    - extra-android-m2repository # for design library
+    - sys-img-armeabi-v7a-addon-google_apis-google-$MIN_SDK_VERSION
+    - sys-img-armeabi-v7a-addon-google_apis-google-$COMPILE_SDK_VERSION
+
+  licenses:
+    - android-sdk-preview-license-.+
+    - android-sdk-license-.+
+    - google-gdk-license-.+
+
+before_script:
+  # Create and start emulator
+  - echo no | android create avd --force -n test -t android-25 --abi armeabi-v7a
+  - emulator -avd test -no-skin -no-audio -no-window &
+  - android-wait-for-emulator
+  - adb shell input keyevent 82 &
+
+script:
+  - "./gradlew clean build connectedCheck -PdisablePreDex --stacktrace"
+
+notifications:
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/0283e844d525908106b2
+    on_success: change  # options: [always|never|change] default: always
+    on_failure: always  # options: [always|never|change] default: always
+    on_start: false     # default: false