The point of `make run` is to abstract away the complexity of `cfx`, so I'd prefer to simply tell people to use `make run` here, since these look like instructions for getting up and running quickly.

But let's add a *Using cfx* section to the end of the document that explains how to activate *cfx* for folks who want more control over their development environment.

And we should also make `make run` reuse a profile directory by default, creating it if it doesn't already exist, something like a top-level *profile* directory that we add to *.gitignore* and delete on `make clean`. I filed issue #317 on that.