Updating Branches to look section to match the current branching stru…

…cture of the project

README.md

@@ -23,4 +23,4 @@ Note that this is build-time requirement.  JDK 5 (for 3.x) or 6 (for 4.0+) is en
 
 ## Branches to look
 
-[The 'master' branch](https://github.com/netty/netty/tree/master) is where the development of the latest major version lives on.  The development of all other versions takes place in each branch whose name is identical to `<majorVersion>.<minorVersion>`.  For example, the development of 3.9 and 4.0 resides in [the branch '3.9'](https://github.com/netty/netty/tree/3.9) and [the branch '4.0'](https://github.com/netty/netty/tree/4.0) respectively.
+Development of all versions takes place in each branch whose name is identical to `<majorVersion>.<minorVersion>`.  For example, the development of 3.9 and 4.0 resides in [the branch '3.9'](https://github.com/netty/netty/tree/3.9) and [the branch '4.0'](https://github.com/netty/netty/tree/4.0) respectively.