Fix split buffer with inconsistently delimited json objects.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

tests/unit/utils_test.py

@@ -0,0 +1,16 @@
+from .. import unittest
+from compose import utils
+
+
+class JsonSplitterTestCase(unittest.TestCase):
+
+    def test_json_splitter_no_object(self):
+        data = '{"foo": "bar'
+        self.assertEqual(utils.json_splitter(data), (None, None))
+
+    def test_json_splitter_with_object(self):
+        data = '{"foo": "bar"}\n  \n{"next": "obj"}'
+        self.assertEqual(
+            utils.json_splitter(data),
+            ({'foo': 'bar'}, '{"next": "obj"}')
+        )