(tracking ticket for https://github.com/mongodb/bson-rust/issues/84)

Currently, when a deserialization error occurs, the error returned by the BSON library identifies the type that was unable to be deserialized, but not the name of the field. This can be ambiguous if there are multiple fields of the same type that are being deserialized. We should investigate how we can improve these error messages, potentially by adding the name of the field and the value that was unable to be deserialized.