Conda constructor wasn't providing enough use to justify its
restrictions:
1. It doesn't work with most of conda-forge due to
https://github.com/conda/constructor/issues/86#issuecomment-330863531.
Almost all the packages we want to ship are in conda-forge.
2. There is no way to pass environment variables to the post-install
script, which makes customization super hard.
3. Can't bundle pip packages, so we need internet access to install
packages anyway. This negates the 'offline installable' aspect of
conda constructor.
4. We need an installer script that users can curl into bash regardless.
Downloading & installing miniconda straight up seems simple enough
for now, and has a reasonable upgrade pathway. I think it'll work out ok!
