Fixing zero-install ipython.py script.

ipython.py

@@ -1,11 +1,12 b''
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 """IPython -- An enhanced Interactive Python
 
 The actual ipython script to be installed with 'python setup.py install' is
 in './scripts' directory. This file is here (ipython source root directory)
 to facilitate non-root 'zero-installation' (just copy the source tree
 somewhere and run ipython.py) and development. """
 
-import IPython.core.shell
-IPython.core.shell.start().mainloop()
+from IPython.core.ipapp import launch_new_instance
+
+launch_new_instance()