Merge pull request #5079 from GobySoft/request-new-extension

Request new option extension (and update URLs for existing projects)

docs/options.md

diff --git a/docs/options.md b/docs/options.md
index f4ea709..700fef6 100644
--- a/docs/options.md
+++ b/docs/options.md
@@ -14,7 +14,7 @@
 ## Existing Registered Extensions
 
 1. C# port of protocol buffers
-   * Website: http://github.com/jskeet/dotnet-protobufs
+   * Website: https://github.com/jskeet/protobuf-csharp-port
    * Extensions: 1000
 
 1. Perl/XS port of protocol buffers