Add way to access fields that is not confused by a '.' in the key names

I ran into a problem today where `Result.Get` wouldn't work, because the key name was a file name, and had a `'.'` in the key name, like so: `{"images":{"image.jpg":{"hash":1234}}}`

When `Result.Get` is called with `"images.image.jpg.hash"`, it causes the call to `strings.Split` to count too many fields, and returns `nil` and not `1234`

This alternative implementation will not have this problem, since it will never need to split, each key is treated as a separate string.

If you like, I can replace the current implementation of `Result.Get` with this one, but it would be a breaking change to all programs currently using the API. This is why I've chosen to submit this as a different function.