Added some regression test

tests/test_exc_info_reference.py

@@ -0,0 +1,26 @@
+alist = []
+
+def app(env, start_response):
+    print 'foo!'
+    print type(start_response)
+    print dir(start_response)
+    c = start_response.__class__
+    try:
+        c()
+    except:
+        import traceback; traceback.print_exc()
+    try:
+        class x(c): pass
+    except:
+        import traceback; traceback.print_exc()
+    start_response('200 alright', [])
+    try:
+        a
+    except:
+        import sys
+        x = sys.exc_info()
+        start_response('500 error', alist, x)
+    return ['hello']
+
+import bjoern
+bjoern.run(app, '0.0.0.0', 8080)