Document correct usage of become_method
So float actually needs to support two authentication scenarios:
- in test environments, log in as unprivileged user ("vagrant" usually), use "sudo" to escalate
- in production environments, log in as root, and we would like not to depend on "sudo" because it is not actually useful in our user-less model
So far we've relied on "sudo" being present by default in the test VM images (as it is in Vagrant's images), but production installations are different and we should have minimal, and explicit, dependencies there. A side effect of the current situation is that "become" won't actually work in production by default, because the default become_method is "sudo".