MAINT: Make split method coarse.

In preparation for removal of widespread events, change the split
methods to use params for sid and cost, instead of an event, for
compatibility with lazy branch.

co-author: @jbredeche <jean@quantopian.com>

zipline/finance/performance/position.py

@@ -82,20 +82,18 @@ class Position(object):
         payment_owed = zp.dividend_payment(out)
         return payment_owed
 
-    def handle_split(self, split):
+    def handle_split(self, sid, ratio):
         """
         Update the position by the split ratio, and return the resulting
         fractional share that will be converted into cash.
 
         Returns the unused cash.
         """
-        if self.sid != split.sid:
+        if self.sid != sid:
             raise Exception("updating split with the wrong sid!")
 
-        ratio = split.ratio
-
-        log.info("handling split for sid = " + str(split.sid) +
-                 ", ratio = " + str(split.ratio))
+        log.info("handling split for sid = " + str(sid) +
+                 ", ratio = " + str(ratio))
         log.info("before split: " + str(self))
 
         # adjust the # of shares by the ratio

zipline/finance/performance/position_tracker.py

@@ -327,7 +327,7 @@ class PositionTracker(object):
             # Make the position object handle the split. It returns the
             # leftover cash from a fractional share, if there is any.
             position = self.positions[split.sid]
-            leftover_cash = position.handle_split(split)
+            leftover_cash = position.handle_split(split.sid, split.ratio)
             self._update_asset(split.sid)
             return leftover_cash