Add repository information to project files

src/Microsoft.AspNet.Antiforgery/project.json

@@ -1,6 +1,10 @@
 {
     "description": "An antiforgery system for ASP.NET designed to generate and validate tokens to prevent Cross-Site Request Forgery attacks.",
     "version": "1.0.0-*",
+    "repository": {
+        "type": "git",
+        "url": "git://github.com/aspnet/antiforgery"
+    },
     "dependencies": {
         "Microsoft.AspNet.DataProtection": "1.0.0-*",
         "Microsoft.AspNet.Http.Abstractions": "1.0.0-*",