Position Tracking

I think this is a good JSON parser, but position tracking could be very handy in debugging. It is hard to find an error in the JSON string when you don't know where it is. Position tracking can be added for example with pos method on JsonReader struct.

[Tpt]

The 0.2 release will replace the std::io::Error error type with SyntaxError that allows to get the error position. I have tagged 0.2.0-alpha.1 that makes this new API accessible. Here is the documentation of the new position access method. Does it covers your use-case?