Merged in "make namespaces work" branch.

Also:
* Fixed inadvertently-omitted `database_cleaner` Gem in Gemfile (and added `pry-rescue`);
* Fixed a howling typo in the README, and polished a couple of points;
* Added generated `Blog` controller/view, tracking Objects on Rails (OoR) p 22;

Still have some weirdness/uncertainty re namespaces: generated controllers went into `app/controllers/blog`, but views into `app/views/blog/blog`. Huh?

RSpec: 4 examples, 0 failures
Script: 0 tests: 0 failures, 0 errors, 0 pending, 0 omitted
RuboCop: 9 files inspected, no offenses detected
RuboCop global overrides in `.rubocop.yml`: 2