Fixing PostsController#index, Part 2

Wherein we actually make sure it *works*, not just that it's connected.
Oops.

RSpec: 1033 examples, 0 failures, 88 pending
RuboCop: 250 files inspected, no offenses detected
PostsController#new now uses Actions::NewPost.

For some reason, earlier specs confused the 'new' and 'create' actions.
Fixed.

RSpec: 1041 examples, 0 failures, 82 pending
RuboCop: 251 files inspected, no offenses detected
Actions::CreatePost wired into PostsController.

With an initially empty view just so the controller specs pass.

RSpec: 1061 examples, 0 failures, 75 pending
RuboCop: 252 files inspected, no offenses detected