Guest viewing member list sees no active/current-user highlight.

Starting to wind down Issue #65.

Also fixed a major malfunction with the `FeatureSpecHelperBase` where it
assumed that its data was an instance of `PostCreatorData`. This also
involved creating a new `UserCreatorData` class. We also needed to
change the existing "member can view other member's profile" spec to
change the way user data was generated; what's now in the `#step` method
is no longer automatic.

RSpec: 635 examples, 0 failures
RuboCop: 147 files inspected, no offenses detected