add whatsnew and uppercase C in load_ext

Use uppercase as this is what is in cython docs.

docs/source/whatsnew/pr/remove_cythonmagic.rst

@@ -0,0 +1,1 b''
+* The ``%cython`` magic, is now part of the Cython module. Use `%load_ext Cython` with a version of Cython >= 0.21 to have acces to the magic now. 

IPython/extensions/cythonmagic.py

@@ -32,7 +32,7 b' def load_ipython_extension(ip):'
     """Load the extension in IPython."""
     
     print("""The Cython magic has been move to the Cython package, hence """)
-    print("""`%load_ext cythonmagic` is deprecated; Please use `%load_ext cython` instead.""")
+    print("""`%load_ext cythonmagic` is deprecated; Please use `%load_ext Cython` instead.""")
     
     if Cython is None or tuple(map(int,Cython.__version__.split('.'))) < (0,21) : 
         print("You need Cython version >=0.21 to use the Cython magic")

docs/source/config/extensions/index.rst

@@ -101,4 +101,4 b' Extensions bundled with IPython'
   ``%load_ext rpy2.ipython`` to load it, and see :mod:`rpy2.ipython.rmagic` for
   details of how to use it.
 * ``cythonmagic``used to be bundled, but is now part of `cython <https://github.com/cython/cython/>`_
-  Use ``%load_ext cython`` to load it.
+  Use ``%load_ext Cython`` to load it.

docs/source/config/intro.rst

@@ -41,7 +41,7 b' extend, :meth:`~IPython.config.loader.LazyConfigValue.prepend` (like'
 extend, but at the front), add and update (which works both for dicts
 and sets)::
 
-    c.InteractiveShellApp.extensions.append('cython')
+    c.InteractiveShellApp.extensions.append('Cython')
 
 .. versionadded:: 2.0
    list, dict and set methods for config values