DictWriter.writeheader should defer to the underlying writer

d27d182 sought to DRY .writeheaders a bit, but introduced a bug.
No diff is too simple for a test, apparently.

unicodecsv/__init__.py

@@ -6,7 +6,7 @@
     izip = zip
 
 #http://semver.org/
-VERSION = (0, 11, 1)
+VERSION = (0, 11, 2)
 __version__ = ".".join(map(str,VERSION))
 
 pass_throughs = [
@@ -154,8 +154,7 @@ def __init__(self, csvfile, fieldnames, restval='', extrasaction='raise', dialec
         self.encoding_errors = errors
 
     def writeheader(self):
-        fieldnames = _stringify_list(self.fieldnames, self.encoding, self.encoding_errors)
-        header = dict(zip(fieldnames, fieldnames))
+        header = dict(zip(self.fieldnames, self.fieldnames))
         self.writerow(header)
 
 class DictReader(csv.DictReader):

unicodecsv/test.py

@@ -599,6 +599,18 @@ def test_write_simple_dict(self):
             fileobj.close()
             os.unlink(name)
 
+    def test_write_unicode_header_dict(self):
+        fd, name = tempfile.mkstemp()
+        fileobj = open(name, 'w+b')
+        try:
+            writer = csv.DictWriter(fileobj, fieldnames = [u"ñ", u"ö"])
+            writer.writeheader()
+            fileobj.seek(0)
+            self.assertEqual(fileobj.readline().decode('utf-8'), u"ñ,ö\r\n")
+        finally:
+            fileobj.close()
+            os.unlink(name)        
+
     def test_write_no_fields(self):
         fileobj = StringIO()
         self.assertRaises(TypeError, csv.DictWriter, fileobj)