CircleCI: Use conda root environment, no need to "activate"

[mgeier]

I didn't like having to call "activate" before each step in my original setup (see #1114).

By installing everything in the "root" environment, we can avoid this.
We also have to save the conda paths etc. in BASH_ENV, for them to be made available in each new task.

[mgeier]

That's the CircleCI log: https://app.circleci.com/jobs/github/mgeier/nbconvert/36

[MSeal]

Running CI tooling as root is generally best avoided if possible, but since the conda env is already owned by root I don't see a problem changing it. Probably better long-term to use a localized environment for the user running the tests, but I'll merge it for now.

[mgeier]

Thanks for merging!

TBH, I don't know whether and how I can change the user. I guess that depends on the used image, right?

I didn't think about changing the user and I didn't notice anyone changing the user in the examples I was consulting.

If you think pursuing this path further is worthwhile please let me know.

[MSeal]

Nah don't worry about it for now. If we get warnings on our builds then we should go take a look again later.