BUG: Forward initialize args and kwargs to user-defined function.

The initialize method of TradingAlgorithm no longer accepts and
silently ignores args and kwargs, but instead forwards them
to the user-defined function referenced by self._initialize.

To avoid passing unexpected arguments to self._initialize, the
following additional adjustments are made:

 - pop 'namespace' from the kwargs supplied to TradingAlgorithm
   rather than simply get()ing it

 - do not pass an AssetFinder to the TradingAlgorithm in
   test_modelling_algo.py, as this has been deprecated and will
   cause self._initialize to fail

zipline/algorithm.py

@@ -177,7 +177,7 @@ class TradingAlgorithm(object):
         self.account_controls = []
 
         self._recorded_vars = {}
-        self.namespace = kwargs.get('namespace', {})
+        self.namespace = kwargs.pop('namespace', {})
 
         self._platform = kwargs.pop('platform', 'zipline')
 
@@ -336,7 +336,7 @@ class TradingAlgorithm(object):
         functions.
         """
         with ZiplineAPI(self):
-            self._initialize(self)
+            self._initialize(self, *args, **kwargs)
 
     def before_trading_start(self, data):
         if self._before_trading_start is None: