System Errors don't seem to have a stack trace

In exploring #2 and gulpjs/async-done#45, I found that [Errors](https://nodejs.org/api/errors.html#errors_system_errors) generated by syscalls (like ENOENT from a fs.stat) don't seem to have a Stack Trace. You can get them to have one by calling `Error.captureStackTrace(err)` but we don't do that on any of our errors that come from node's `fs` module.

@erikkemperman @contra @terinjokes do ya'll think we should capture stack traces before forwarding the errors? It's pretty annoying to track down `Error: ENOENT: no such file or directory, stat '/Users/phated/test/testcase-vinyl-bug/outbad'`