Print stack trace for errors

[danielb2]

> try { JSON.parse("") } catch (e) { console.log(e); }
SyntaxError: Unexpected end of JSON input
    at Object.parse (native)
    at repl:1:12
    at sigintHandlersWrap (vm.js:22:35)
    at sigintHandlersWrap (vm.js:73:12)
    at ContextifyScript.Script.runInThisContext (vm.js:21:12)
    at REPLServer.defaultEval (repl.js:340:29)
    at bound (domain.js:280:14)
    at REPLServer.runBound [as eval] (domain.js:293:12)
    at REPLServer.<anonymous> (repl.js:539:10)
    at emitOne (events.js:96:13)
undefined
> p = require('purdy')
{ [Function] stringify: [Function] }
[Atry { JSON.parse("") } catch (e) { p(e); }
[SyntaxError: Unexpected end of JSON input]

Purdy is too sparse here