Add copyright to new file

src/main/scala/com/amazon/deequ/analyzers/RatioOfSums.scala

@@ -1,3 +1,19 @@
+/**
+ * Copyright 2018 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. A copy of the License
+ * is located at
+ *
+ *     http://aws.amazon.com/apache2.0/
+ *
+ * or in the "license" file accompanying this file. This file 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.
+ *
+ */
+
 package com.amazon.deequ.analyzers
 
 import com.amazon.deequ.analyzers.Preconditions.{hasColumn, isNumeric}