Correctly detect unref'ed handles

At this point, Timeout objects aren't the only handles that have a
hasRef() method. nodejs/node#42756 added
hasRef() to the Worker handle object that gets reported by async_hooks,
so we should consider that too.

Fixes: #59
Signed-off-by: Darshan Sen <raisinten@gmail.com>

index.js

@@ -27,7 +27,6 @@ function whyIsNodeRunning (logger) {
   hook.disable()
   var activeResources = [...active.values()].filter(function(r) {
     if (
-      r.type === 'Timeout' &&
       typeof r.resource.hasRef === 'function'
       && !r.resource.hasRef()
     ) return false