Make query iterator class public.

See:
#487 (comment)

gcloud/datastore/query.py

@@ -315,12 +315,12 @@ def fetch(self, limit=0, offset=0, start_cursor=None, end_cursor=None):
         :type end_cursor: offset
         :param end_cursor: An optional cursor passed through to the iterator.
 
-        :rtype: :class:`_Iterator`
+        :rtype: :class:`Iterator`
         """
-        return _Iterator(self, limit, offset, start_cursor, end_cursor)
+        return Iterator(self, limit, offset, start_cursor, end_cursor)
 
 
-class _Iterator(object):
+class Iterator(object):
     """Represent the state of a given execution of a Query.
     """
     _NOT_FINISHED = datastore_pb.QueryResultBatch.NOT_FINISHED

gcloud/datastore/test_query.py

@@ -412,7 +412,7 @@ def test_group_by(self):
                          ['a', 'b', 'c'])
 
 
-class Test_Iterator(unittest2.TestCase):
+class TestIterator(unittest2.TestCase):
     _DATASET = 'DATASET'
     _NAMESPACE = 'NAMESPACE'
     _KIND = 'KIND'
@@ -430,8 +430,8 @@ def tearDown(self):
         _implicit_environ.DATASET = self._replaced_dataset
 
     def _getTargetClass(self):
-        from gcloud.datastore.query import _Iterator
-        return _Iterator
+        from gcloud.datastore.query import Iterator
+        return Iterator
 
     def _makeOne(self, *args, **kw):
         return self._getTargetClass()(*args, **kw)