DOC: cleanup Usage section

[drux007]

Under Usage section, I noticed:

deactivate               # deactivate the current active environment

is shown three times. Not sure how I didn't notice it last time ^^

This pull request cleans it up.

[hagenw]

Now I get it. It was also the reason why envs was there more than one time. The current usage section does not simply list all commands, but provides an example of a possible workflow. For that reason it deactivates more than one environment.

I'm not sure yet if we should change to listing all commands and adding a small example afterwards?

[drux007]

Ahaa now I get it!

It wasn't clear to me from the beginning. I came here to search for the commands first.

So maybe by splitting it into 2 sections where we:

• list all available commands
• add possible workflow

would be clearer.