add missing licence header, singa logo and stargazers chart

README.md

@@ -16,6 +16,9 @@
     specific language governing permissions and limitations
     under the License.
 -->
+
+![Logo](doc/_static/singa.png)
+
 # Apache SINGA
 
 [![Build Status](https://travis-ci.org/apache/singa.png)](https://travis-ci.org/apache/singa)
@@ -41,6 +44,8 @@ Distributed deep learning system
 ![LGTM C++ Grade](https://img.shields.io/lgtm/grade/cpp/github/apache/incubator-singa)
 ![LGTM Python Grade](https://img.shields.io/lgtm/grade/python/github/apache/incubator-singa)
 
+[![Stargazers over time](https://starchart.cc/apache/singa.svg)](https://starchart.cc/apache/singa)
+
 ## Mailing Lists
 
 * [Development Mailing List](mailto:[email protected]) ([Archive](http://mail-archives.apache.org/mod_mbox/singa-dev/))

SECURITY.md

@@ -1,3 +1,22 @@
+<!--
+    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.
+-->
+
 # Security Policy
 
 ## Reporting a Vulnerability