PostsController#index action added.

At its most basic. No functioning index view as yet.

RSpec: 838 examples, 0 failures (but see Issue #87)
RuboCop: 161 files inspected, no offenses detected
Posts in index now filtered by Pundit policy.

Policy itself had Scope class enclosed per docs. This was the missing
bit that somehow hadn't filtered in the first dozen times I read the
doc.

RSpec: 841 examples, 0 failures (but see Issue #87)
RuboCop: 161 files inspected, no offenses detected
Alternate fix using existing Blog controller.

The whole point of Use Case 3 on Issue #52 is to have draft posts
visible to the author, but only to the author. Technically, this commit
satisfies that requirement.

This is FUGLY code that should NEVER see the light of day beyond barest
proof-of-concept. The view helper for one controller/view salmagundi
(BlogHelper) still knows much too much too much about the workings of
the PostData model.  Issue #109 will solve this, and should be
completed.

But it's nice to see drafts listed when the author is logged in, then
log out and see them disappear from the index. Ah well.

RSpec: 841 examples, 0 failures (but see Issue #87)
RuboCop: 161 files inspected, no offenses detected
More #summarise_blog cleanup.

We really are getting somewhere here; this needs to move.

RSpec: 841 examples, 0 failures (but see Issue #87)
RuboCop: 161 files inspected, no offenses detected
Decoupled BlogSummariser from its base logic.

New `BaseSummariser` class has all the core logic and DSL support of
the previous `BlogSummariser`, with no application-specific (Blog- or
PostData-related) knowledge.

RSpec: 841 examples, 0 failures (but see Issue #87)
RuboCop: 161 files inspected, no offenses detected
Decoupled BaseSummariser from BlogSummariser.

Next up: taking the BlogSummariser code (used by BlogController#index)
and creating a workalike PostsSummariser (for PostsController#index)
before killing the Blog stuff.

RSpec: 854 examples, 0 failures (but see Issue #87)
RuboCop: 163 files inspected, no offenses detected
PostsSummariser transplants BlogSummariser

We're getting close to eliminating implementation-level Blog code now.

RSpec: 866 examples, 0 failures (but see Issue #87)
RuboCop: 164 files inspected, no offenses detected
App root now 'posts#index'.

The `posts#index` view now renders a page identical to the
still-existing `blog#index` view.

Now to rip out the Blog stuff.

RSpec: 866 examples, 0 failures (but see Issue #87)
RuboCop: 164 files inspected, no offenses detected
[Closes #109] Ripped out BlogData-related code.

The `Blog` domain entity still lives, but the controller, model (and
underlying database table), helpers, views and corresponding specs are
gone.

RSpec: 810 examples, 0 failures (but see Issue #87)
RuboCop: 152 files inspected, no offenses detected
Merge pull request #110 from jdickey/issue-109

[Closes #109] Eliminating BlogData (and BlogController, etc.)

The `BlogData` is gone; long live the `Blog` data!

Still some cleanup left to do in The Glorious Future™; see, e.g., [`PostCreatorAndPublisher#create_params`](https://github.com/jdickey/new_poc/blob/b5b5c8d/app/interactors/post_creator_and_publisher.rb#L34-L38), but specs pass (including feature specs), and ad hoc testing looks good.

Onward!

RSpec: 810 examples, 0 failures (but see Issue #87)
RuboCop: 152 files inspected, no offenses detected