Update Rails from 5.1.5 to 5.2.0.

We don't tie to Rails as a whole, so in practice this is bumping:

* actionpack
* actionview
* activemodel
* activerecord
* activesupport
* arel
* railties

Gemfile.lock

@@ -16,28 +16,28 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    actionpack (5.1.5)
-      actionview (= 5.1.5)
-      activesupport (= 5.1.5)
+    actionpack (5.2.1)
+      actionview (= 5.2.1)
+      activesupport (= 5.2.1)
       rack (~> 2.0)
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.2)
-    actionview (5.1.5)
-      activesupport (= 5.1.5)
+    actionview (5.2.1)
+      activesupport (= 5.2.1)
       builder (~> 3.1)
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.3)
-    activemodel (5.1.5)
-      activesupport (= 5.1.5)
-    activerecord (5.1.5)
-      activemodel (= 5.1.5)
-      activesupport (= 5.1.5)
-      arel (~> 8.0)
-    activesupport (5.1.5)
+    activemodel (5.2.1)
+      activesupport (= 5.2.1)
+    activerecord (5.2.1)
+      activemodel (= 5.2.1)
+      activesupport (= 5.2.1)
+      arel (>= 9.0)
+    activesupport (5.2.1)
       concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (~> 0.7)
+      i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
     addressable (2.5.2)
@@ -52,7 +52,7 @@ GEM
       bundler
       rake
       thor (>= 0.14.0)
-    arel (8.0.0)
+    arel (9.0.0)
     ast (2.4.0)
     autoprefixer-rails (8.0.0)
       execjs
@@ -103,7 +103,7 @@ GEM
       activesupport (>= 4.2.0)
     hashdiff (0.3.7)
     highline (2.0.0)
-    i18n (0.9.5)
+    i18n (1.1.0)
       concurrent-ruby (~> 1.0)
     i18n-tasks (0.9.24)
       activesupport (>= 4.0.2)
@@ -170,12 +170,12 @@ GEM
     rails-html-sanitizer (1.0.4)
       loofah (~> 2.2, >= 2.2.2)
     rails_stdout_logging (0.0.5)
-    railties (5.1.5)
-      actionpack (= 5.1.5)
-      activesupport (= 5.1.5)
+    railties (5.2.1)
+      actionpack (= 5.2.1)
+      activesupport (= 5.2.1)
       method_source
       rake (>= 0.8.7)
-      thor (>= 0.18.1, < 2.0)
+      thor (>= 0.19.0, < 2.0)
     rainbow (3.0.0)
     raindrops (0.19.0)
     rake (12.3.1)