Show JSON path

Hi AST Explorer is fantastic but trying to keep all the nodes straight in my head is darn near impossible. Could you add a status field somewhere that shows the JSON path to the currently selected element, something like http://jsonpathfinder.com/ ?

Also it would be really fantastic to be able to enter a JSON path and have it select/highlight that node. I realize this is a little complex though so just showing the path would provide most of the functionality I need.

Oh and as far as JSON path string standards on this go, `JSONPath.stringify()` works ok. Otherwise you could just show the path in bracket form `['some']['path']['here']` and use JSON.stringify() to quote each node's name for display between the brackets.

Thanks for your hard work so far!

No files, tests, or entry points are named. Start by tracing how AST Explorer tracks the currently selected AST element and where status information is rendered; done means the selected node's JSON path is displayed, with the requested path-entry selection treated as optional scope.

Written by the indexing model from the issue text.