utility to wrap error calling async's into error throwing async's
for these throwier times... (or at least for versions of node that include domains)
turn a node-style (exception ...rest) callback into a (...rest) callback that throws
var throwify = ;var fs = ;var stat = ;;
handling node-style error callbacks injects complexity into almost everything you'll write. often it's convenient and possible to wrap a discrete chunk of code in a domain and localize the exception handling there.