Update README to reflect 2.0 default testing

Added some details to the addition of `distutil` tests introduced in 2.0.  Since we have scripted testing, it seems useful for users to make sure their installation is working.

@seancribbs See if this is reasonable or not. I'm happy to revise in any direction you see fit.
Let's just remove this, it is no longer relevant. Our dependencies are set up properly.