add documentation for ReactiveUI view bindings

Hi,
I have been playing with ReactiveUI's view bindings, and I really like it. I wrote some documentation for the view bindings, and they should be correct (as far as I can tell from the source). 

I have also noticed that some parameters were ignored or not passed through correctly (although I am not sure given my unfamiliarity with the source), should I send a pull request to discuss those?

Thanks