Specify how we prompt for the SAS comparison

We don't want to get too much into UI concerns here, but we've defined
a behavior for an SAS mismatch, so we need to be sure an
implementation makes this possible by allowing the user to indicate
that the words did not match.
Add sections for Secure and Not Secure states

We mention the conditions for these states in the mental security
model, but we should also break these out into more normative
sections.
Release v0.5