Update CONTRIBUTING.md (vNext -> 5)

CONTRIBUTING.md

@@ -23,8 +23,8 @@ Or browse the full list of repos in the [aspnet](https://github.com/aspnet/) org
 ## Other discussions
 Our team members also monitor several other discussion forums:
 
-* [ASP.NET vNext forum](http://forums.asp.net/1255.aspx/1?ASP+NET+vNext)
-* [StackOverflow](http://stackoverflow.com/questions/tagged/asp.net-vnext) with the `asp.net-vnext` or `entity-framework-7` tag
+* [ASP.NET 5 forum](http://forums.asp.net/1255.aspx/1?ASP+NET+5)
+* [StackOverflow](http://stackoverflow.com/questions/tagged/asp.net-5) with the `asp.net-5` or `entity-framework-7` tag
 * [JabbR chat room](https://jabbr.net/#/rooms/aspnetvnext) for real-time discussions with the community and the people who work on the project