Remove support for Rails < 5.2 (#377)

Author: bensheldon

.github/workflows/test.yml

@@ -30,15 +30,10 @@ jobs:
           - redis
           - active_record
         gemfile:
-          - gemfiles/rails42.gemfile
-          - gemfiles/rails42_protected_attributes.gemfile
-          - gemfiles/rails51.gemfile
           - gemfiles/rails52.gemfile
           - gemfiles/rails60.gemfile
           - gemfiles/rails61.gemfile
-        exclude:
-          - ruby: jruby-9.1.13.0
-            gemfile: gemfiles/rails5.gemfile
+
     env:
       DB: ${{ matrix.db }}
       BUNDLE_GEMFILE: ${{ github.workspace }}/${{ matrix.gemfile }}

Appraisals

@@ -1,34 +1,12 @@
-appraise "rails42" do
-  gem "mocha", "~> 1.0", require: false
-  gem "rails", "4.2.9"
-  gem "fastthread", github: "zoltankiss/fastthread", platforms: :mri_20
-  gem "passenger"
-end
-
-appraise "rails42-protected_attributes" do
-  gem "protected_attributes", "1.1.0"
-  gem "mocha", "~> 1.0", require: false
-  gem "rails", "4.2.9"
-  gem "fastthread", github: "zoltankiss/fastthread", platforms: :mri_20
-  gem "passenger"
-end
-
-appraise "rails51" do
-  gem "mocha",  "~> 1.0", require: false
-  gem "rails", "~>5.1.0"
-  gem "fastthread", github: "zoltankiss/fastthread", platforms: :mri_20
-  gem "passenger"
-end
-
 appraise "rails52" do
-  gem "mocha",  "~> 1.0", require: false
+  gem "mocha", "~> 1.0", require: false
   gem "rails", "~>5.2.0"
   gem "fastthread", github: "zoltankiss/fastthread", platforms: :mri_20
   gem "passenger"
 end
 
 appraise "rails60" do
-  gem "mocha",  "~> 1.0", require: false
+  gem "mocha", "~> 1.0", require: false
   gem "rails", "~>5.2.0"
   gem "fastthread", github: "zoltankiss/fastthread", platforms: :mri_20
   gem "passenger"

README.md

@@ -380,15 +380,10 @@ your view no participants will be recorded.
 
 Here's what's tested and known to work:
 
-    Ruby 2.3
-      Persistence: Redis (redis-rb >= 3.2.1), Mongo, ActiveRecord
-      Rails: 4.1, 4.2, 5
-    Ruby 2.4
-      Persistence: Redis (redis-rb >= 3.2.1), Mongo, ActiveRecord
-      Rails: 4.1, 4.2, 5
-    JRuby 9.1
-      Persistence: Redis (redis-rb >= 3.2.1), Mongo, ActiveRecord
-      Rails: 4.1, 4.2
+    Rails: 5.2+
+    Ruby: 2.5+
+    JRuby: 9.1+
+    Persistence: Redis (redis-rb >= 3.2.1), Mongo, ActiveRecord
 
 ## Testing