verify that top-level tests can be defined asynchronously

This was an issue wiht TAP 0.x which I was reminded of recently.

Since the rewrite, it's not a problem, because the underlying code
was completely obliterated and designed in a cleaner way.  However,
it's always good to keep the ratchets around, so this test is here
to prevent back-sliding on this issue.

Author: isaacs

test/test/async.js

@@ -0,0 +1,13 @@
+var t = require('../..')
+
+t.test('first test', function (t) {
+  t.pass('this is ok')
+  t.end()
+})
+
+setTimeout(function () {
+  t.test('second test (async)', function (t) {
+    t.pass('this is ok')
+    t.end()
+  })
+})

test/test/async.tap

@@ -0,0 +1,14 @@
+TAP version 13
+    # Subtest: first test
+    ok 1 - this is ok
+    1..1
+ok 1 - first test ___/# time=[0-9.]+(ms)?/~~~
+
+    # Subtest: second test (async)
+    ok 1 - this is ok
+    1..1
+ok 2 - second test (async) ___/# time=[0-9.]+(ms)?/~~~
+
+1..2
+___/# time=[0-9.]+(ms)?/~~~
+