Fix prerender server returning status other than 200, which caused the middleware to bomb out, and the normal request pipeline continued. Now the WebException is handled and the correct status code (such as 404 etc.) is passed to the client along with the prerendered content from the server
Merge pull request #3 from mgoodfellow/master

Fix prerender server returning status other than 200, which caused the m...

@mgoodfellow  thanks.