Removed Ruby 2.2 for support version

Author: hsbt

.travis.yml

@@ -1,7 +1,6 @@
 sudo: false
 language: ruby
 rvm:
-  - 2.2.7
   - 2.3.5
   - 2.4.2
   - ruby-head

gdbm.gemspec

@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
   spec.extensions    = ["ext/gdbm/extconf.rb"]
-  spec.required_ruby_version = ">= 2.2.2"
+  spec.required_ruby_version = ">= 2.3.0"
 
   spec.add_development_dependency "bundler", "~> 1.14"
   spec.add_development_dependency "rake", "~> 10.0"