add LICENSE for StringUtils.java. alibaba#2007

NOTICE

@@ -10,3 +10,18 @@ The greys-anatomy Project
 =================
 Please visit Github for more information:
   * https://github.com/oldmanpushcart/greys-anatomy 
+
+
+-------------------------------------------------------------------------------
+This product contains a modified portion of 'Apache Commons Lang':
+  * LICENSE:
+    * Apache License 2.0
+  * HOMEPAGE:
+    * https://commons.apache.org/proper/commons-lang/
+
+
+This product contains a modified portion of 'Apache Commons Net':
+  * LICENSE:
+    * Apache License 2.0
+  * HOMEPAGE:
+    * https://commons.apache.org/proper/commons-net/

core/src/main/java/com/taobao/arthas/core/util/StringUtils.java

@@ -1,3 +1,19 @@
+/*
+ * 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.
+ */
 package com.taobao.arthas.core.util;
 
 import java.io.BufferedReader;