Don't try to pass shell up kwargs from Magics class

See ipython/traitlets#176 - this is causing test failures.

IPython/core/magic.py

@@ -516,11 +516,11 @@ def __init__(self, shell=None, **kwargs):
             raise ValueError('Magics subclass without registration - '
                              'did you forget to apply @magics_class?')
         if shell is not None:
+            self.shell = shell
             if hasattr(shell, 'configurables'):
                 shell.configurables.append(self)
             if hasattr(shell, 'config'):
                 kwargs.setdefault('parent', shell)
-            kwargs['shell'] = shell
 
         self.shell = shell
         self.options_table = {}