update install instruction

docs/source/install/kernel_install.rst

@@ -1,51 +1,60 b''
 .. _kernel_install:
 
 Installing the IPython kernel
 =============================
 
 IPython can be installed (different python versions, virtualenv or conda
 environments) as a kernel for Jupyter by following these steps:
 
 * make sure that the desired python installation is active
   (e.g. activate the environment, or use absolute paths)
   and ipykernel is installed
 * run once ``ipython kernel install --user``,
   or ``python -m ipykernel install --user`` to ensure a specific Python installation is used.
+* See `ipython kernel install --help` for the list of installation options like
+  naming the kernel, or non default install location.
+* The IPython kernel for Jupyter is provided by the `ipykernel` python package,
+  see there if you need more flexibility for installation.
 
 
-The last command installs a :ref:`kernel spec <jupyterclient:kernelspecs>` file for the current python installation. Kernel spec files are JSON files, which can be viewed and changed with a
-normal text editor.
+The last command installs a :ref:`kernel spec <jupyterclient:kernelspecs>` file
+for the current python installation. Kernel spec files are JSON files, which
+can be viewed and changed with a normal text editor.
 
 For example:
 
 .. sourcecode:: bash
 
     source activate kernel-environment
     ipython kernel install --user
     source deactivate kernel-environment
 
 or
 
 .. sourcecode:: bash
 
     ~/envs/kernel-environment/python -m ipykernel install --user
 
+.. note ::
+
+    The command `ipython kernelspec` is deprecated and will be removed in future versions.
+
 
 .. _multiple_kernel_install:
 
 Multiple IPython installs
 =========================
 
 If you want to have multiple IPython kernels for different environments,
 you will need to specify unique names for the kernelspecs,
 and you may also want to specify the display name of those kernels,
 so that you can clearly see which is which in the notebook menus:
 
 .. sourcecode:: bash
 
     source activate myenv
     ipython kernel install --user --name myenv --display-name "Python (myenv)"
     source activate other-env
     ipython kernel install --user --name other-env --display-name "Python (other-env)"
     source deactivate