Add support for repeated timestamps and durations to to_dict from_dict (#211)

tests/inputs/repeated_duration_timestamp/test_repeated_duration_timestamp.py

@@ -0,0 +1,9 @@
+from datetime import datetime, timedelta
+
+from tests.output_betterproto.repeated_duration_timestamp import Test
+
+
+def test_roundtrip():
+    message = Test()
+    message.times = [datetime.now(), datetime.now()]
+    message.durations = [timedelta(), timedelta()]