Non-compliant for `/foo/01` and `/foo/-`

[emilbayes]

The pointers /foo/01 and /foo/- do not yet seem to be implemented here. I made a quick implementation here: https://gist.github.com/emilbayes/e6b740529147a72205f0

[janl]

@emilbayes wanna send a pull request? :)

[emilbayes]

Hehe, I considered it, but it seemed like too much work trying to understand your implementation, hence the commented gist :)

[janl]

I don’t have time to transform the code. If you want to see this in the project, I need something that I can merge :)

[marcbachmann]

According to the RFC, leading zeros aren't allowed.
http://tools.ietf.org/html/rfc6901#section-4

o If the currently referenced value is a JSON array, the reference
token MUST contain either:

 *  characters comprised of digits (see ABNF below; note that
    leading zeros are not allowed) that represent an unsigned
    base-10 integer value, making the new referenced value the
    array element with the zero-based index identified by the
    token, or

 *  exactly the single character "-", making the new referenced
    value the (non-existant) member after the last array element.

The ABNF syntax for array indices is:

array-index = %x30 / ( %x31-39 *(%x30-39) )
; "0", or digits without a leading "0"

[marcbachmann]

IMO we can close this.

Concerning the error handling:
This library currently returns null when a pointer references a non-existing value.
According to the spec this behavior can vary between implementations and should be documented.

https://tools.ietf.org/html/rfc6901#section-7

1. Error Handling

In the event of an error condition, evaluation of the JSON Pointer
fails to complete.

Error conditions include, but are not limited to:

o Invalid pointer syntax

o A pointer that references a nonexistent value

This specification does not define how errors are handled. An
application of JSON Pointer SHOULD specify the impact and handling of
each type of error.

For example, some applications might stop pointer processing upon an
error, while others may attempt to recover from missing values by
inserting default ones.