[filipesantoss]

Fixes #16

Summary

Reads and deletes look up the reference token as a JavaScript property lookup does.

Writes accept only an array index or - for an array.
Writes throw a TypeError with the cursor for any other token.

 get / unset / remove (token)
-  key = computeSegment(token)                    # parseInt for an array
-  if value has own property key
+  if value has own enumerable property token     # items, not an array's length
     read or delete it

 set / assign (token)
   computeSegment(value, token, location)
     if value is an array and token is "-"
       return value.length
-    return parseInt(token, 10)
+    if token is not "0" or digits without a leading "0"
+      throw TypeError "Value at '<cursor>' is an array and '<token>' is not a valid array index"
+    return Number(token)

Merge Danger

A token such as 01 no longer reaches item 1.
A caller that wrote through such a token now gets an error.
A write with a token that is not a number, such as foo, also throws.