Resolve #329, add copyright agreement statement on README and LICENSE

LICENSE

 BSD 3-Clause License
 
-Copyright (c) 2016 - 2019 360 Enterprise Security Group, Endpoint Security,
-inc. All rights reserved.
+Copyright (c) 2016-2019, 360 Enterprise Security Group, Endpoint Security, Inc.
+Copyright (c) 2011-2017, Geoffrey J. Teale (complying with the tealeg/xlsx license)
+All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
@@ -13,7 +14,7 @@ modification, are permitted provided that the following conditions are met:
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.
 
-* Neither the name of Excelize nor the names of its
+* Neither the name of the copyright holder nor the names of its
   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.
 

README.md

@@ -168,12 +168,14 @@ func main() {
 
 Contributions are welcome! Open a pull request to fix a bug, or open an issue to discuss a new feature or change. XML is compliant with [part 1 of the 5th edition of the ECMA-376 Standard for Office Open XML](http://www.ecma-international.org/publications/standards/Ecma-376.htm).
 
-## Credits
-
-Some struct of XML originally by [tealeg/xlsx](https://github.com/tealeg/xlsx).
-
 ## Licenses
 
 This program is under the terms of the BSD 3-Clause License. See [https://opensource.org/licenses/BSD-3-Clause](https://opensource.org/licenses/BSD-3-Clause).
 
+The Excel logo is a trademark of [Microsoft Corporation](https://aka.ms/trademarks-usage). This artwork is an adaptation.
+
+Some struct of XML originally by [tealeg/xlsx](https://github.com/tealeg/xlsx). Licensed under the [BSD 3-Clause License](https://github.com/tealeg/xlsx/blob/master/LICENSE).
+
+gopher.{ai,svg,png} was created by [Takuya Ueda](https://twitter.com/tenntenn). Licensed under the [Creative Commons 3.0 Attributions license](http://creativecommons.org/licenses/by/3.0/).
+
 [![FOSSA Status](https://app.fossa.io/api/projects/git%2Bgithub.com%2F360EntSecGroup-Skylar%2Fexcelize.svg?type=large)](https://app.fossa.io/projects/git%2Bgithub.com%2F360EntSecGroup-Skylar%2Fexcelize?ref=badge_large)

README_zh.md

@@ -168,12 +168,14 @@ func main() {
 
 欢迎您为此项目贡献代码，提出建议或问题、修复 Bug 以及参与讨论对新功能的想法。 XML 符合标准： [part 1 of the 5th edition of the ECMA-376 Standard for Office Open XML](http://www.ecma-international.org/publications/standards/Ecma-376.htm)。
 
-## 致谢
-
-本类库中部分 XML 结构体的定义参考了开源项目：[tealeg/xlsx](https://github.com/tealeg/xlsx).
-
 ## 开源许可
 
 本项目遵循 BSD 3-Clause 开源许可协议，访问 [https://opensource.org/licenses/BSD-3-Clause](https://opensource.org/licenses/BSD-3-Clause) 查看许可协议文件。
 
+Excel 徽标是 [Microsoft Corporation](https://aka.ms/trademarks-usage) 的商标，项目的图片是一种改编。
+
+本类库中部分 XML 结构体的定义参考了开源项目：[tealeg/xlsx](https://github.com/tealeg/xlsx)，遵循 [BSD 3-Clause License](https://github.com/tealeg/xlsx/blob/master/LICENSE) 开源许可协议。
+
+gopher.{ai,svg,png} 由 [Takuya Ueda](https://twitter.com/tenntenn) 创作，遵循 [Creative Commons 3.0 Attributions license](http://creativecommons.org/licenses/by/3.0/) 创作共用授权条款。
+
 [![FOSSA Status](https://app.fossa.io/api/projects/git%2Bgithub.com%2F360EntSecGroup-Skylar%2Fexcelize.svg?type=large)](https://app.fossa.io/projects/git%2Bgithub.com%2F360EntSecGroup-Skylar%2Fexcelize?ref=badge_large)