drop support for Rubies < 2.1.0

.rubocop.yml

@@ -36,16 +36,11 @@ Style/AlignArray:
   Exclude:
     - spec/integration_spec.rb
 
-# Rubocop suggests using $INPUT_RECORD_SEPARATOR
-# variable from stdlib 'English' module over $/.
-# This module appeared in Ruby 2.0, so we could use it
-# only if we drop 1.9.3 support
-Style/SpecialGlobalVars:
-  Exclude:
-    - interactor.gemspec
-
 # This could be removed if throws are used instead of
 # raising Failure in #fail!
 Lint/HandleExceptions:
   Exclude:
     - lib/interactor.rb
+
+AllCops:
+  TargetRubyVersion: 2.1

.travis.yml

@@ -20,8 +20,6 @@ notifications:
     urls:
       - http://buildlight.collectiveidea.com/
 rvm:
-  - 1.9.3
-  - "2.0"
   - "2.1"
   - "2.2"
   - "2.3.3"

interactor.gemspec

@@ -1,4 +1,5 @@
 # encoding: utf-8
+require "English"
 
 Gem::Specification.new do |spec|
   spec.name    = "interactor"
@@ -12,9 +13,11 @@ Gem::Specification.new do |spec|
   spec.homepage    = "https://github.com/collectiveidea/interactor"
   spec.license     = "MIT"
 
-  spec.files      = `git ls-files`.split($/)
+  spec.files      = `git ls-files`.split($INPUT_RECORD_SEPARATOR)
   spec.test_files = spec.files.grep(/^spec/)
 
+  spec.required_ruby_version = ">= 2.1"
+
   spec.add_development_dependency "bundler", "~> 1.7"
   spec.add_development_dependency "rake", "~> 10.3"
   spec.add_development_dependency "rubocop", "~> 0.47.1"