Update Sidekiq from 4.2.1 to 4.2.7.

Includes various bug fixes, mostly for Rails 5.

Changelog: https://github.com/mperham/sidekiq/blob/fc168fe393bee3ad1fcbb52cff2d84af86c38cc4/Changes.md

Gemfile

@@ -132,7 +132,7 @@ gem 'after_commit_queue', '~> 1.3.0'
 gem 'acts-as-taggable-on', '~> 4.0'
 # Background jobs
-gem 'sidekiq', '~> 4.2'
+gem 'sidekiq', '~> 4.2.7'
 gem 'sidekiq-cron', '~> 0.4.4'
 gem 'redis-namespace', '~> 1.5.2'
 gem 'sidekiq-limit_fetch', '~> 3.4'

Gemfile.lock

@@ -126,7 +126,7 @@ GEM
     coffee-script-source (1.10.0)
     colorize (0.7.7)
     concurrent-ruby (1.0.2)
-    connection_pool (2.2.0)
+    connection_pool (2.2.1)
     crack (0.4.3)
       safe_yaml (~> 1.0.0)
     creole (0.5.0)
@@ -648,10 +648,10 @@ GEM
       rack
     shoulda-matchers (2.8.0)
       activesupport (>= 3.0.0)
-    sidekiq (4.2.1)
+    sidekiq (4.2.7)
       concurrent-ruby (~> 1.0)
       connection_pool (~> 2.2, >= 2.2.0)
-      rack-protection (~> 1.5)
+      rack-protection (>= 1.5.0)
       redis (~> 3.2, >= 3.2.1)
     sidekiq-cron (0.4.4)
       redis-namespace (>= 1.5.2)
@@ -928,7 +928,7 @@ DEPENDENCIES
   settingslogic (~> 2.0.9)
   sham_rack (~> 1.3.6)
   shoulda-matchers (~> 2.8.0)
-  sidekiq (~> 4.2)
+  sidekiq (~> 4.2.7)
   sidekiq-cron (~> 0.4.4)
   sidekiq-limit_fetch (~> 3.4)
   simplecov (= 0.12.0)