Update authorization.markdown

Removed the instruction to reference Raven.Bundles.Authorization.dll since referencing both the client and the server version of the bundle gives a compile error. Also this brings this file in line with http://ravendb.net/docs/article-page/3.0/csharp/client-api/bundles/how-to-work-with-authorization-bundle.
Merge pull request #99 from philipkaare/patch-1

Update authorization.markdown