BUG: Ensure that correct dates are emitted during entire minute rate.

Also, fix double emission of performance results with the last minute.

Change the perf tracker unit tests so that it doesn't rely on an
'extra' event triggering emission.
Unlike daily, minute emission now emits at the end of the bar in
the PerformanceTracker.transform instead of waiting for the next event.

tests/test_perf_tracking.py

@@ -1060,28 +1060,34 @@ class TestPerformanceTracker(unittest.TestCase):
         bar_event_2 = factory.create_trade(
             'bar', 11.0, 20, start_dt + datetime.timedelta(minutes=1))
 
-        foo_event_3 = factory.create_trade(
-            'foo', 12.0, 30, start_dt + datetime.timedelta(minutes=2))
+        events = [
+            foo_event_1,
+            bar_event_1,
+            foo_event_2,
+            bar_event_2
+        ]
 
-        tracker.process_event(foo_event_1)
-        tracker.process_event(bar_event_1)
-        messages = tracker.process_event(foo_event_2)
-        tracker.process_event(bar_event_2)
-        messages += tracker.process_event(foo_event_3)
+        import operator
+        messages = {date: snapshot[0].perf_messages[0] for date, snapshot in
+                    tracker.transform(
+                        itertools.groupby(
+                            events,
+                            operator.attrgetter('dt')))}
 
         self.assertEquals(2, len(messages))
 
-        self.assertEquals(1, len(messages[0]['intraday_perf']['transactions']),
+        msg_1 = messages[foo_event_1.dt]
+        msg_2 = messages[foo_event_2.dt]
+
+        self.assertEquals(1, len(msg_1['intraday_perf']['transactions']),
                           "The first message should contain one transaction.")
         # Check that transactions aren't emitted for previous events.
-        self.assertEquals(0, len(messages[1]['intraday_perf']['transactions']),
+        self.assertEquals(0, len(msg_2['intraday_perf']['transactions']),
                           "The second message should have no transactions.")
 
         # Ensure that period_close moves through time.
         # Also, ensure that the period_closes are the expected dts.
         self.assertEquals(foo_event_1.dt,
-                          messages[0]['intraday_perf']['period_close'],
-                          messages[0])
+                          msg_1['intraday_perf']['period_close'])
         self.assertEquals(foo_event_2.dt,
-                          messages[1]['intraday_perf']['period_close'],
-                          messages[1])
+                          msg_2['intraday_perf']['period_close'])