Changes test factory to use Event instead of ndict.

As more sources are moving off of ndict,
changing the factory to use Event, so that when testing we are
exercising use of Event.

zipline/protocol.py

@@ -50,5 +50,8 @@ class Event(object):
     def __eq__(self, other):
         return self.__dict__ == other.__dict__
 
+    def __contains__(self, name):
+        return name in self.__dict__
+
     def __repr__(self):
         return "Event({0})".format(self.__dict__)

zipline/utils/factory.py

@@ -30,7 +30,7 @@ from datetime import datetime, timedelta
 
 import zipline.finance.risk as risk
 from zipline.utils.date_utils import tuple_to_date
-from zipline.utils.protocol_utils import ndict
+from zipline.protocol import Event
 from zipline.sources import (SpecificEquityTrades,
                              DataFrameSource,
                              DataPanelSource)
@@ -144,7 +144,7 @@ def create_trade_history(sid, prices, amounts, interval, trading_calendar,
 
 
 def create_txn(sid, price, amount, datetime):
-    txn = ndict({
+    txn = Event({
         'sid': sid,
         'amount': amount,
         'dt': datetime,