Bump shoulda-matchers from 4.1.2 to 4.2.0 (#1519)

Bumps [shoulda-matchers](https://github.com/thoughtbot/shoulda-matchers) from 4.1.2 to 4.2.0.
- [Release notes](https://github.com/thoughtbot/shoulda-matchers/releases)
- [Changelog](https://github.com/thoughtbot/shoulda-matchers/blob/master/NEWS.md)
- [Commits](thoughtbot/shoulda-matchers@v4.1.2...v4.2.0)

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

Gemfile.lock

@@ -103,7 +103,7 @@ GEM
       activesupport (>= 4.2.0)
     hashdiff (1.0.0)
     highline (2.0.2)
-    i18n (1.7.0)
+    i18n (1.7.1)
       concurrent-ruby (~> 1.0)
     i18n-tasks (0.9.29)
       activesupport (>= 4.0.2)
@@ -213,7 +213,7 @@ GEM
     selectize-rails (0.12.6)
     sentry-raven (2.13.0)
       faraday (>= 0.7.6, < 1.0)
-    shoulda-matchers (4.1.2)
+    shoulda-matchers (4.2.0)
       activesupport (>= 4.2.0)
     sprockets (4.0.0)
       concurrent-ruby (~> 1.0)
@@ -228,7 +228,7 @@ GEM
     thread_safe (0.3.6)
     tilt (2.0.10)
     timecop (0.9.1)
-    tzinfo (1.2.5)
+    tzinfo (1.2.6)
       thread_safe (~> 0.1)
     uglifier (4.2.0)
       execjs (>= 0.3.0, < 3)