Update view api

Updates based on comments in https://github.com/kite-sdk/kite-docs/pull/63 .
> The only restriction is that you can't make a change that could potentially corrupt the underlying dataset.

I'm not sure what you mean here, but I think the idea is coming from the restricted writes. The behavior is specific to reading or writing, so let's cover it in those sections. Here, we should mention that it's just like interacting with a Dataset because you use newReader and newWriter to get the same reader or writer object, but one that is restricted to the view.