Given:

```
import argonaut._, Argonaut._

case class Person(name: String)

implicit def decode: DecodeJson[Person] =
  DecodeJson ( c => 
    for {
      name <- (c --\ "name").as[String]
    } yield Person(name)
  )

scala> Parse.decode[Person]("""{"name": "Bob", "foo": "dunno"}""")
res5: Either[Either[String,(String, argonaut.CursorHistory)],Person] = 
  Right(Person(Bob))

```

How can I `decode`, i.e. `JSON => Person`, with the cursor's history? By history, I mean, I'd like to know that `"foo" : "dunno"` was not looked at/traversed.