Added remaining trading system around portfolio in order to compare with OANDA.

event/event.py

@@ -0,0 +1,28 @@
+class Event(object):
+    pass
+
+
+class TickEvent(Event):
+    def __init__(self, instrument, time, bid, ask):
+        self.type = 'TICK'
+        self.instrument = instrument
+        self.time = time
+        self.bid = bid
+        self.ask = ask
+
+
+class SignalEvent(Event):
+    def __init__(self, instrument, order_type, side):
+        self.type = 'SIGNAL'
+        self.instrument = instrument
+        self.order_type = order_type
+        self.side = side        
+
+
+class OrderEvent(Event):
+    def __init__(self, instrument, units, order_type, side):
+        self.type = 'ORDER'
+        self.instrument = instrument
+        self.units = units
+        self.order_type = order_type
+        self.side = side