Change install docs to use --user

This changes the install docs to use `pip install --user` instead of
`pip install --install-option="--user"`. `--user` is indeed the option
to use for a user-scheme installation.

See http://pip.readthedocs.org/en/latest/user_guide.html#user-installs.

Author: elemoine

docs/source/install.rst

@@ -104,12 +104,12 @@ or::
 
 An alternative to installing it into the global site-packages is to
 add it to `your user local directory
-<http://docs.python.org/install/index.html#alternate-installation-the-home-scheme>`__
+<http://docs.python.org/install/index.html#alternate-installation-the-user-scheme>`__
 (usually `~/.local`).
 
 ::
 
-  $ pip install --install-option="--user" virtualenvwrapper
+  $ pip install --user virtualenvwrapper
 
 .. _install-shell-config: