Bump shoulda-matchers and shoulda

Bumps [shoulda-matchers](https://github.com/thoughtbot/shoulda-matchers) and [shoulda](https://github.com/thoughtbot/shoulda). These dependencies needed to be updated together.

Updates `shoulda-matchers` from 3.1.3 to 4.5.1
- [Release notes](https://github.com/thoughtbot/shoulda-matchers/releases)
- [Changelog](https://github.com/thoughtbot/shoulda-matchers/blob/master/CHANGELOG.md)
- [Commits](thoughtbot/shoulda-matchers@v3.1.3...v4.5.1)

Updates `shoulda` from 3.6.0 to 4.0.0
- [Release notes](https://github.com/thoughtbot/shoulda/releases)
- [Changelog](https://github.com/thoughtbot/shoulda/blob/master/CHANGELOG.md)
- [Commits](thoughtbot/shoulda@v3.6.0...v4.0.0)

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile

@@ -35,7 +35,7 @@ end
 
 group :test do
   gem 'simplecov', require: false
-  gem 'shoulda', '~> 3.5'
+  gem 'shoulda', '~> 4.0'
   gem 'shoulda-matchers'
   gem 'rails-controller-testing'
 end

Gemfile.lock

@@ -204,12 +204,12 @@ GEM
       sprockets (> 3.0)
       sprockets-rails
       tilt
-    shoulda (3.6.0)
-      shoulda-context (~> 1.0, >= 1.0.1)
-      shoulda-matchers (~> 3.0)
-    shoulda-context (1.2.2)
-    shoulda-matchers (3.1.3)
-      activesupport (>= 4.0.0)
+    shoulda (4.0.0)
+      shoulda-context (~> 2.0)
+      shoulda-matchers (~> 4.0)
+    shoulda-context (2.0.0)
+    shoulda-matchers (4.5.1)
+      activesupport (>= 4.2.0)
     simplecov (0.18.5)
       docile (~> 1.1)
       simplecov-html (~> 0.11)
@@ -277,7 +277,7 @@ DEPENDENCIES
   rails-controller-testing
   rspec-rails (~> 4.0.2)
   sass-rails (~> 6.0)
-  shoulda (~> 3.5)
+  shoulda (~> 4.0)
   shoulda-matchers
   simplecov
   slim-rails