moved everything into Prerender.io namespace, consolidated with NuGet pa...

...ckage

Someone published NuGet package for this ASP.NET middleware but source code was never synced with it.
Please accept this pull request to make everything a bit more clean and consolidated.

Also consider renaming the repo to something more sensible (Prerender_asp_mvc is misleading because it's a module that works with other ASP.NET flavours too).

HTH