Merge pull request #13232 from strzalek/av-missing-requires

Require action_view explicitly in AC::Base
Upgrade minitest version

We made a change in #13213 that depends on a new file that's only in
minitest 5.1.0+, so the version should be updated.
Merge pull request #13231 from chancancode/upgrade_minitest

Upgrade minitest version
Merge pull request #13235 from strzalek/variants-inline

Inline syntax for variants
Revert "Merge pull request #13235 from strzalek/variants-inline" -- needs a little more work!

This reverts commit 186161148a189839a1e0924043f068a8d155ce69, reversing
changes made to cad9eb178ea5eec0e27d74e93518f4ed34e2f997.
Inline variants syntax

In most cases, when setting variant specific code, you're not sharing any code
within format.

Inline syntax can vastly simplify defining variants in those situations:

  respond_to do |format|
    format.js { render "trash" }
    format.html do |variant|
      variant.phone { redirect_to progress_path }
      variant.none  { render "trash" }
    end
  end

Becomes:

  respond_to do |format|
    format.js         { render "trash" }
    format.html.phone { redirect_to progress_path }
    format.html.none  { render "trash" }
  end