Bump ruby requirement

.rubocop.yml

@@ -1,7 +1,7 @@
 # Defaults can be found here: https://github.com/bbatsov/rubocop/blob/master/config/default.yml
 
 AllCops:
-  TargetRubyVersion: 2.1
+  TargetRubyVersion: 2.2
   Exclude:
     - 'spec/fixtures/**/*'
     - 'lib/danger/plugin_support/plugin_parser.rb'

.travis.yml

@@ -4,10 +4,10 @@ cache:
     - bundle
 
 rvm:
-  - 2.4.0
-  - 2.3.3
-  - 2.1.9
-  - 2.0
+  - 2.2.8
+  - 2.3.5
+  - 2.4.2
+  - ruby-head
 
 before_install:
   - gem install bundler

danger-jazzy.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ['lib']
 
-  spec.required_ruby_version = '>= 2.0.0'
+  spec.required_ruby_version = '>= 2.2'
 
   spec.add_runtime_dependency 'danger-plugin-api', '~> 1.0'
   spec.add_runtime_dependency 'json', '~> 2.1.0'
@@ -31,9 +31,10 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rspec', '~> 3.4'
 
   # Linting code and docs
+  spec.add_development_dependency 'coveralls', '~> 0.8.15'
   spec.add_development_dependency 'rubocop', '~> 0.52.1'
   spec.add_development_dependency 'yard', '~> 0.9.12'
-  spec.add_development_dependency 'coveralls', '~> 0.8.15'
+
 
   # Makes testing easy via `bundle exec guard`
   spec.add_development_dependency 'guard', '~> 2.14'