Pickle fix for SortedSet on py27

Author: grantjenks

sortedcontainers/sortedset.py

@@ -702,7 +702,7 @@ def __reduce__(self):
         confuse pickle so customize the reducer.
 
         """
-        return (type(self)._fromset, (self._set, self._key))
+        return (type(self), (self._set, self._key))
 
 
     @recursive_repr()

tests/test_coverage_sortedset.py

@@ -473,6 +473,7 @@ def test_pickle():
     import pickle
     alpha = SortedSet(range(10000), key=negate)
     alpha._reset(500)
-    beta = pickle.loads(pickle.dumps(alpha))
+    data = pickle.dumps(alpha)
+    beta = pickle.loads(data)
     assert alpha == beta
     assert alpha._key == beta._key