Require Ruby 2.2+

Missed in 6ca4ed8.

Author: sds

overcommit.gemspec

@@ -25,7 +25,7 @@ Gem::Specification.new do |s|
                             Dir['libexec/**/*'] +
                             Dir['template-dir/**/*']
 
-  s.required_ruby_version = '>= 2.1'
+  s.required_ruby_version = '>= 2.2'
 
   s.add_dependency          'childprocess', '~> 0.6', '>= 0.6.3'
   s.add_dependency          'iniparse', '~> 1.4'