add travis config

Author: gyeongil-goo

.travis.yml

@@ -0,0 +1,44 @@
+language: java
+matrix:
+  include:
+    - name: Java 11
+      jdk: openjdk11
+      before_install: source ./.travis.install_jdk.sh
+      env:
+      - TEST_JAVA_VERSION=11
+      - TRAVIS_GRADLE_PROPERTIES=-Pcoverage
+      after_success:
+        - bash <(curl -s https://codecov.io/bash)
+    - name: Java 13
+      before_install: source ./.travis.install_jdk.sh 13
+      env: TEST_JAVA_VERSION=13
+    - name: Java 8
+      jdk: openjdk8
+      before_install: source ./.travis.install_jdk.sh
+      env: TEST_JAVA_VERSION=8
+sudo: false
+os:
+- linux
+branches:
+  only:
+  - master
+cache:
+  directories:
+  - "$HOME/.cache/yarn"
+  - "$HOME/.gradle/wrapper/dists"
+  - "$HOME/.gradle/caches/jars-3"
+  - "$HOME/.gradle/caches/modules-2"
+  - "$HOME/.gradle/caches/package-lists"
+  - "$HOME/.gradle/caches/sphinx-binary"
+  - "$HOME/.jdk"
+env:
+  global:
+  - "_JAVA_OPTIONS=-Djavax.net.ssl.trustStore=/etc/ssl/certs/java/cacerts"
+install:
+- true
+script:
+- "./gradlew --version"
+- "./gradlew --no-daemon --stacktrace --warning-mode=all ${TRAVIS_GRADLE_PROPERTIES} check"
+before_cache:
+- find $HOME/.gradle/caches -name '*.lock' -delete
+