Clarify installation recommendation with Conda

[ambrosejcarr]

We currently recommend installation of cellxgene in conda using pip, which is brittle to scientists installing additional packages using conda install.

Friederike Dundar suggests that we either maintain a conda recipe such as this one so that we can update the installation instructions to include conda install, or clarify that it is risky to mix pip and conda installation commands.

[ambrosejcarr]

@MaximilianLombardo we should update our documentation to clarify that only cellxgene should be installed in its conda environment to avoid additional packages installed on top breaking the cellxgene installation. I don't think it's necessary to maintain a recipe since cellxgene does not need to be co-imported with other python packages to function (users can use one environment for scanpy, jupyter, etc, and a second for cellxgene).

[signechambers1]

@MaximilianLombardo is this still worth doing? Let's incorporate it or if it's too low priority close.

[MaximilianLombardo]

Let's keep this open. I will be getting to this topic during my docs rewrite towards the beginning of this quarter. We can close once this section of the docs is updated.

[signechambers1]

@MaximilianLombardo can this ticket be closed now?