remove parallelmagic extension from docs

docs/source/config/extensions/index.txt

@@ -1,78 +1,77
 .. _extensions_overview:
 
 ==================
 IPython extensions
 ==================
 
 Configuration files are just the first level of customization that IPython
 supports. The next level is that of extensions. An IPython extension is an
 importable Python module that has a a few special function. By defining these
 functions, users can customize IPython by accessing the actual runtime objects
 of IPython.  Here is a sample extension::
 
     # myextension.py
 
     def load_ipython_extension(ipython):
         # The ``ipython`` argument is the currently active 
         # :class:`InteractiveShell` instance that can be used in any way.
         # This allows you do to things like register new magics, plugins or
         # aliases.
 
     def unload_ipython_extension(ipython):
         # If you want your extension to be unloadable, put that logic here.
 
 This :func:`load_ipython_extension` function is called after your extension is
 imported and the currently active :class:`InteractiveShell` instance is passed
 as the only argument. You can do anything you want with IPython at that point.
 
 The :func:`load_ipython_extension` will be called again is you load or reload
 the extension again. It is up to the extension author to add code to manage
 that.
 
 Useful :class:`InteractiveShell` methods include :meth:`~IPython.core.interactiveshell.InteractiveShell.define_magic`, 
 :meth:`~IPython.core.interactiveshell.InteractiveShell.push` (to add variables to the user namespace) and 
 :meth:`~IPython.core.interactiveshell.InteractiveShell.drop_by_id` (to remove variables on unloading).
 
 You can put your extension modules anywhere you want, as long as they can be
 imported by Python's standard import mechanism. However, to make it easy to
 write extensions, you can also put your extensions in
 ``os.path.join(self.ipython_dir, 'extensions')``. This directory is added to
 ``sys.path`` automatically.
 
 Using extensions
 ================
 
 There are two ways you can tell IPython to use your extension:
 
 1. Listing it in a configuration file.
 2. Using the ``%load_ext`` magic function.
 
 To load an extension called :file:`myextension.py` add the following logic
 to your configuration file::
 
     c.InteractiveShellApp.extensions = [
         'myextension'
     ]
 
 To load that same extension at runtime, use the ``%load_ext`` magic:
 
 .. sourcecode:: ipython
 
     In [1]: %load_ext myextension
 
 To summarize, in conjunction with configuration files and profiles, IPython
 extensions give you complete and flexible control over your IPython
 setup.
 
 Extensions bundled with IPython
 ===============================
 
 .. toctree::
    :maxdepth: 1
 
    autoreload
    cythonmagic
-   parallelmagic
    rmagic
    storemagic
    sympyprinting