Suggest current best practice of %pip install control #1113

I suggest on your main README the following change to suggest the use of the magic pip install:

%pip install control

DETAILS

You suggest on your main README the following:

!pip install control

In 2019 the magic %pip install command was added and is a better thing to suggest these days as it leads to less issues since it installs to the correct environment where the kernel is running. Because it fails to do this, the exclamation point version can lead to issues.