add branch list to readme

README.md

@@ -5,3 +5,9 @@ The code samples from my microservices book - https://manning.com/books/microser
 
 ## About the book
 Microservices in .NET Core shows you how to build and deploy secure and operations-friendly microservices using Nancy. The book takes you through an introduction to the microservices architectural style. Next, you'll learn important practical aspects of developing microservices from simple core concepts to more sophisticated. Throughout the book, you'll see many code examples implementing it with lightweight .NET technologies—most prominently Nancy. By the end, you'll be able to quickly and easily build reliable and operations-friendly microservices using Nancy, OWIN and other open technologies.
+
+## Branches
+From time to time I will update the code use newer versions of libraries as well as .NET Core. I will keep each such update in a branch. The brances in the repository are:
+
+ * `master`: The code as it appears in the book
+ * `2017-05`: Everything updated to use `csproj` files instead of `project.json` files, so it's compatible with Visual Studio 2017 and newer `dotnet` command line versions. Furhtermore everything is updated to .NET Core 1.1 and Nancy 2.0.0-clinteastwood.