Merge pull request #51 from alpacahq/allOrdersHotfix

fixing incorrect timestamp format going into trading_calendars

pylivetrader/backend/alpaca.py

@@ -300,7 +300,7 @@ def all_orders(self, before=None, status='all', days_back=None):
         # A session label refers to the market date that an order submitted
         # at a given minute would be executed on. We'll need to keep track of
         # this if the function is bounded by days_back.
-        start_session_label = self._cal.minute_to_session_label(start)
+        start_session_label = self._cal.minute_to_session_label(now)
         reached_end_date = False
 
         all_orders = {}