Fixed tsv auto format detection.

tablib/formats/_csv.py

@@ -49,7 +49,7 @@ def import_set(dset, in_stream, headers=True):
 def detect(stream):
     """Returns True if given stream is valid CSV."""
     try:
-        csv.Sniffer().sniff(stream)
+        csv.Sniffer().sniff(stream, delimiters=',')
         return True
     except (csv.Error, TypeError):
         return False

test_tablib.py

@@ -494,10 +494,12 @@ class TablibTestCase(unittest.TestCase):
         _yaml = '- {age: 90, first_name: John, last_name: Adams}'
         _json = '[{"last_name": "Adams","age": 90,"first_name": "John"}]'
         _csv = '1,2,3\n4,5,6\n7,8,9\n'
+        _tsv = '1\t2\t3\n4\t5\t6\n7\t8\t9\n'
         _bunk = '¡¡¡¡¡¡---///\n\n\n¡¡£™∞¢£§∞§¶•¶ª∞¶•ªº••ª–º§•†•§º¶•†¥ª–º•§ƒø¥¨©πƒø†ˆ¥ç©¨√øˆ¥≈†ƒ¥ç©ø¨çˆ¥ƒçø¶'
 
         self.assertEqual(tablib.detect(_yaml)[0], tablib.formats.yaml)
         self.assertEqual(tablib.detect(_csv)[0], tablib.formats.csv)
+        self.assertEqual(tablib.detect(_tsv)[0], tablib.formats.tsv)
         self.assertEqual(tablib.detect(_json)[0], tablib.formats.json)
         self.assertEqual(tablib.detect(_bunk)[0], None)