Implemented ShouldRenderFileContents and deprecated ShouldRenderFile

I have implemented the `ShouldRenderFileContents` method and it's relevant overloads and I have marked the `ShouldRenderFile` method as obsolete. 

I did *not* implement support for the overload that takes a string. I want to implement that overload but first I would like to validate that this code is correct. 

Thanks.