Set up CI with Azure Pipelines

[drivendata]

No description provided.

[pjbull]

Working on this on top of #162 instead so that the new comprehensive tests there can get run against all of the platforms.

[jayqi]

So the only remaining failing tests are for virtualenvwrapper on Windows. Tried a bunch of things and not able to get them working. The gist of the problem is that which virtualenvwrapper.sh does not work. virtualenvwrapper is installed, and the directory containing that script is in $PATH, but it does not turn up with which because it's not executable. I've tried the following:

• Using find to search all $PATH directories to grab it.
  • Sourcing it directly helps, but there's a source `which virtualenvwrapper.sh` in the Makefile as well.
  • Not able to chmod it to be executable because I guess that's a Windows file system limitation.
  • Adding a #!/bin/bash shebang to the first line (which it doesn't have); I tested this on the AWS Workspace machine, and this worked there in making Git Bash recognize the file as an executable. Don't know why it doesn't work on Azure Pipelines.
• Tried installing virtualenvwrapper-win. That didn't seem to do anything.

I think what I would recommend is using find to grab the path of virtualenvwrapper.sh and sourcing that, and then removing the source `which virtualenvwrapper.sh` from Makefile. That would require users to have properly sourced it in the .bash_profile or whatever, instead of CCDS doing it for them.