Streamline autocompletion explanations in readme

Important details about Bash were not mentioned in our explanation. Furthermore,
these instructions may get obsolete at any moment. Better to delegate to the
argcomplete project.

readme.md

@@ -92,9 +92,7 @@ The second starts with a bang: `!`, and is treated as a shell command.
 
 ## Autocompletion
 
-For autocompletion to work, you need the [argcomplete](https://argcomplete.readthedocs.io) python package.
+For autocompletion to work, you need the [argcomplete](https://argcomplete.readthedocs.io) Python package, and Bash 4.2 or newer. For activating *bash* or *tsch* completion, consult the [argcomplete documentation](https://argcomplete.readthedocs.io/en/latest/#global-completion).
-
-For *bash* completion, just activate it globally with the command `activate-global-python-argcomplete`, or `activate-global-python-argcomplete --user`, that will copy `python-argcomplete.sh` to `/etc/bash_completion.d/` or `~/.bash_completion.d/`. You need to make sure that the file is evaluated on bash start. For more information or other shells please report to [argcomplete's documentation](https://argcomplete.readthedocs.io).
 
 For *zsh* completion, the global activation is not supported but bash completion compatibility can be used for pubs. For that, add the following to your `.zshrc`: