BUG: Fix volume value returned by daily spot price

Volumes were incorrectly having the thousands factor applied, however
the volume is written as is (without the factor, since it volume is an
int, not float value.)

Fix by adding a special case for volume which returns the price as is.

tests/data/test_us_equity_pricing.py

@@ -291,6 +291,11 @@ class BcolzDailyBarTestCase(TestCase):
                                   'close')
         self.assertEqual(235651.0, price)
 
+        # Ensure that volume does not have float adjustment applied.
+        volume = reader.spot_price(1, Timestamp('2015-06-02', tz='UTC'),
+                                   'volume')
+        self.assertEqual(145631, volume)
+
     def test_unadjusted_spot_price_no_data(self):
         table = self.writer.write(self.dest, self.trading_days, self.assets)
         reader = BcolzDailyBarReader(table)

zipline/data/us_equity_pricing.py

@@ -498,7 +498,11 @@ class BcolzDailyBarReader(object):
             raise NoDataOnDate(
                 "No data on or after day={0} for sid={1}".format(
                     day, sid))
-        return self._spot_col(colname)[ix] * 0.001
+        price = self._spot_col(colname)[ix]
+        if colname != 'volume':
+            return price * 0.001
+        else:
+            return price
 
 
 class SQLiteAdjustmentWriter(object):