Update README.md

README.md

 # spdlog
 
-Very fast, header-only/compiled, C++ logging library. [![Build Status](https://app.travis-ci.com/gabime/spdlog.svg?branch=v1.x)](https://app.travis-ci.com/gabime/spdlog)  [![Build status](https://ci.appveyor.com/api/projects/status/d2jnxclg20vd0o50?svg=true)](https://ci.appveyor.com/project/gabime/spdlog) [![Release](https://img.shields.io/github/release/gabime/spdlog.svg)](https://github.com/gabime/spdlog/releases/latest)
+Very fast, header-only/compiled, C++ logging library. [![Build Status](https://app.travis-ci.com/gabime/spdlog.svg?branch=v2.x)](https://app.travis-ci.com/gabime/spdlog)  [![Build status](https://ci.appveyor.com/api/projects/status/d2jnxclg20vd0o50?svg=true&branch=v2.x)](https://ci.appveyor.com/project/gabime/spdlog) [![Release](https://img.shields.io/github/release/gabime/spdlog.svg)](https://github.com/gabime/spdlog/releases/latest)
 
 ## Install 
 #### Header only version
-Copy the include [folder](https://github.com/gabime/spdlog/tree/v1.x/include/spdlog) to your build tree and use a C++11 compiler.
+Copy the include [folder](https://github.com/gabime/spdlog/tree/v2.x/include/spdlog) to your build tree and use a C++1r compiler.
 
 #### Static lib version (recommended - much faster compile times)
 ```console