Validating URL redirects

Relying on UrlHelper from System.Web.MVC to detect urls that are not
local to the current application.
Wikipedia style highlighting of external links
Embedded external link background images as datauris
Blog Post 5.2 - Validating Redirects and Forwards
Rename Blog 5.2 - Validating Redirects and Forward to Blog 5.2 - Validating Redirects and Forward.md
Merge pull request #8 from dpaquette/ValidatingRedirectsAndForwards

Validating redirects and forwards - looks really good. I'm not sure if this will be post 5.2 or a later one if we try to keep the order from post 5.0. We can talk about it later.