Move test_thread over to unittest. Commits GHOP 237.

Thanks Benjamin Peterson for the patch.
diff --git a/Misc/NEWS b/Misc/NEWS
index 4d0b9f0..e316c13 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -50,6 +50,8 @@
 Tests
 -----
 
+- GHOP 237: Rewrite test_thread using unittest.
+
 - Patch #2232: os.tmpfile might fail on Windows if the user has no
   permission to create files in the root directory.