ENH: Send transactions and orders as standalone events.

- Add transaction and order types
- Move TransactionSimulator from trading.py to tradesimulation.py
  (only used by other members of the tradesimulation module)
- Make Transaction an independent event, like dividend
- Add Blotter class.
- Flatten the transaction events to be independent of trade bar events
- Make orders into events that reach performance (need to add
handling)
- Issue IDs to orders and tracking each transaction's order id.
- Make volume share slippage fill orders independently, rather than
  aggregating them into a single transaction.
- Perf tracker holds orders, serializes them with transactions.
- Order state defined and maintained by order class.
- Minutely emission of orders based on last_modified date.

tests/test_algorithm_gen.py

@@ -66,10 +66,12 @@ class TestAlgo(TradingAlgorithm):
 
             self.ordered = True
 
-        self.asserter.assertGreaterEqual(
-            self.latest_date,
-            self.slippage.latest_date
-        )
+        else:
+
+            self.asserter.assertGreaterEqual(
+                self.latest_date,
+                self.slippage.latest_date
+            )
 
 
 class AlgorithmGeneratorTestCase(TestCase):