Drop support for older ruby versions less than 2.6

Update development dependencies

.github/workflows/create_release.yml

@@ -6,7 +6,7 @@ on:
 
 jobs:
   release:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
     - name: Checkout code
       uses: actions/checkout@v2

.github/workflows/lint.yml

@@ -2,7 +2,7 @@ name: Lint
 on: [push, pull_request]
 jobs:
   lint:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
     - name: Set up Ruby 2.7

.github/workflows/tests.yml

@@ -2,10 +2,10 @@ name: Tests
 on: [push, pull_request]
 jobs:
   test:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
-        ruby: [2.4, 2.5, 2.6, 2.7, 3.0]
+        ruby: [2.6, 2.7, 3.0, 3.1]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Ruby

.rubocop.yml

@@ -10,7 +10,7 @@ AllCops:
     - 'benchmark/circuit_store_benchmark.rb'
     - 'ci/Gemfile'
   NewCops: enable
-  TargetRubyVersion: 2.4
+  TargetRubyVersion: 2.6
 
 Layout/LineLength:
   Enabled: false

.ruby-version

@@ -1 +1 @@
-2.7.2
+2.7.4

Gemfile

@@ -7,7 +7,7 @@ gemspec
 
 gem "pry"
 
-gem 'rubocop', '~> 1.12.1', require: false
-gem 'rubocop-minitest', '~> 0.12.1', require: false
-gem 'rubocop-performance', '~> 1.11.3', require: false
-gem 'rubocop-rake', '~> 0.5.1', require: false
+gem 'rubocop', '~> 1.25.0', require: false
+gem 'rubocop-minitest', '~> 0.17.0', require: false
+gem 'rubocop-performance', '~> 1.13.0', require: false
+gem 'rubocop-rake', '~> 0.6.0', require: false

circuitbox.gemspec

@@ -16,15 +16,16 @@ Gem::Specification.new do |spec|
   spec.metadata = {
     'bug_tracker_uri' => 'https://github.com/yammer/circuitbox/issues',
     'changelog_uri' => 'https://github.com/yammer/circuitbox/blob/main/CHANGELOG.md',
-    'source_code_uri' => 'https://github.com/yammer/circuitbox'
+    'source_code_uri' => 'https://github.com/yammer/circuitbox',
+    'rubygems_mfa_required' => 'true'
   }
 
-  spec.required_ruby_version = '>= 2.4.0'
+  spec.required_ruby_version = '>= 2.6.0'
 
   spec.files = Dir['README.md', 'LICENSE', 'lib/**/*']
   spec.require_paths = ['lib']
 
-  spec.add_development_dependency 'bundler', '> 1.16'
+  spec.add_development_dependency 'bundler', '> 2.0'
   spec.add_development_dependency 'excon', '~> 0.71'
   spec.add_development_dependency 'faraday', ['>= 0.8', '< 2.0']
   spec.add_development_dependency 'gimme', '~> 0.5'