fix bug de serialising partial paths

do not assume all paths start at index zero for the last item when doing
the de serialize (this lets us set part of an array by specifying the
index and the count, ie {...,"path":"something.something[1]", "value":
[1,2], "count":3,...}
Merge pull request #11 from othane/fix_deserialise_partial_array

fix bug de serialising partial paths