Drop the support of ruby 2.2

since we encounter Segmentation fault and have no idea how to fix it

The error messages:

Installing Bundler
  /opt/hostedtoolcache/Ruby/2.2.10/x64/bin/gem install bundler -v 1.17.3
  /opt/hostedtoolcache/Ruby/2.2.10/x64/lib/ruby/2.2.0/rubygems/source.rb:192: [BUG] Segmentation fault at 0x00000000000010
  ruby 2.2.10p489 (2018-03-28 revision 63023) [x86_64-linux]

.github/workflows/ruby.yml

@@ -20,7 +20,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby:
-          - 2.2
+          - 2.3
           - 2.6
           - 2.7
         gemfile:
@@ -38,7 +38,7 @@ jobs:
           - gemfile: 4.2.gemfile
             ruby: 2.7
           - gemfile: 6.0.gemfile
-            ruby: 2.2
+            ruby: 2.3
     env:
       BUNDLE_GEMFILE: "gemfiles/${{ matrix.gemfile }}"
 

README.md

@@ -12,9 +12,13 @@ ActiveModelCachers:
 
 - Uses multiple levels of cache ([Multi-level Cache](#multi-level-cache))
 - Does not pollute the original ActiveModel API
-- Supports ActiveRecord 3.2, 4.2, 5.2, 6.0.
 - Has high test coverage
 
+## Supports
+
+- Ruby 2.3 ~ 2.7
+- Rails 3.2, 4.2, 5.0, 5.1, 5.2, 6.0
+
 ## Table of contents
 
 1. [Compare with identity_cache](#compare-with-identity_cache)