[FLINK-15851] [build] Add .travis.yml for Travis CI setup

This closes apache#10.

.travis.yml

@@ -0,0 +1,29 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+dist: xenial
+
+language: java
+
+jobs:
+  include:
+    - if: type in (pull_request, push)
+      jdk: "openjdk8"
+      script: mvn clean install
+      name: build - jdk8
+    - if: type in (pull_request, push)
+      jdk: "openjdk11"
+      script: mvn clean install
+      name: build - jdk11