check header in checkstyle (#7)

Author: davecramer

config/checkstyle/amazon.header

@@ -0,0 +1,17 @@
+/*
+ *
+ *     Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ *     Licensed 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.
+ *
+ */

config/checkstyle/google_checks.xml

@@ -369,4 +369,8 @@
             <property name="optional" value="true"/>
         </module>
     </module>
+    <module name="Header">
+        <property name="headerFile" value="config/checkstyle/amazon.header"/>
+        <property name="fileExtensions" value="java"/>
+    </module>
 </module>