Add Travis YAML file (.travis.yml) to build on Travis CI.

.travis.yml

@@ -0,0 +1,16 @@
+language: java
+
+os:
+  - linux
+
+jdk:
+  - oraclejdk8
+
+script: ./gradlew build
+
+before_cache:
+  - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
+cache:
+  directories:
+    - $HOME/.gradle/caches/
+    - $HOME/.gradle/wrapper/