Correct docstring of ipython.py

The script installed by setup.py is auto-generated by distutils.

Fixes  #2858.

ipython.py

@@ -3,9 +3,11 b''
 """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. """
+generated by distutils via the `console_scripts` mechanism.  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.
+
+"""
 
 if __name__ != "__main__":
     raise RuntimeError('You are trying to import the ipython.py executable. '
@@ -20,4 +22,3 b' sys.path.insert(0, this_dir)'
 execfile(os.path.join(
     this_dir, 'IPython', 'scripts', 'ipython'
 ))
-