Change `sudo pip install` to `pip install --user`

You never need elevated permissions for pip. To install at the user level, use the `--user` flag.

There is too much wanton use of `sudo` online, we all need to collectively be more careful about the instructions we provide to users.

Thanks for this linter!

README.rst

@@ -54,7 +54,7 @@ Alternatively using pip, the Python package manager:
 
 .. code:: bash
 
- sudo pip install yamllint
+ pip install --user yamllint
 
 Usage
 ^^^^^