Finishing up user bio/profile as rich content.

* First, see the relatively simple change made to the FactoryGirl
`:user_datum` factory in `spec/factories/user_data.rb`; the `profile`
field now has a Markdown-italicised word in it. Simple, but sufficient
to help show that Markdown-persisted content is rendered properly.
* Next, look at the Users :show template in
`app/views/users/show.slim`. Besides deleting some previously
commented-out crap, the call to the `#profile_bio_panel` helper
function passes in `user.build_profile` rather than the previous
`user.profile`. This translates the Markdown content in the `:profile`
attribute into HTML and passes it to the helper, which expects HTML.
* The spec for `UserDataDecorator` should be pretty self-explanatory;
kick the tires on the golden path for the `:build_profile` method.
* Finally, the updated
`spec/features/member_can_view_own_profile_page_spec.rb` verifies that
the HTML-rendered profile content is properly included in the profile
page.

Pinging Issue #72.

RSpec: 507 examples, 0 failures
RuboCop: 131 files inspected, no offenses detected