Update the "tested up to" version, fixes #85
Properly update user roles when changing settings.

Before we changed all users mapped to Memberful with the old
role, rather than checking if they actually deserved the new role.

This new approach is slower, but more accurate. Ideally we could push
this update into a background job, but alas WordPress doesn't support
them.
Ensure Role decision object is bult correctly.
Changing stable version number to 1.6.2