update link to the Manning site

Author: rkuhn

README.md

@@ -1,6 +1,6 @@
 # Reactive Design Patterns Code Samples
 
-This repository hosts the code samples that are used in [Reactive Design Patterns](http://manning.com/kuhn) for illustration. We aim at full test coverage to make sure that the code that we present actually works. While we tend to start out with writing Scala or Java code, we want this repository to also hold samples in other languages (like JavaScript, Ruby, Python, etc.). Contributions, corrections, wishes and all kind of help is appreciated, please don’t hesitate to use the issue tracker.
+This repository hosts the code samples that are used in [Reactive Design Patterns](https://www.manning.com/books/reactive-design-patterns) for illustration. We aim at full test coverage to make sure that the code that we present actually works. While we tend to start out with writing Scala or Java code, we want this repository to also hold samples in other languages (like JavaScript, Ruby, Python, etc.). Contributions, corrections, wishes and all kind of help is appreciated, please don’t hesitate to use the issue tracker.
 
 ## Legal