polyfill.gemspec in polyfill-1.6.0 vs polyfill.gemspec in polyfill-1.7.0

@@ -1,8 +1,6 @@
-# coding: utf-8
-
-lib = File.expand_path('../lib', __FILE__)
+lib = File.expand_path('lib', __dir__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'polyfill/version'
 
 Gem::Specification.new do |spec|
   spec.name    = 'polyfill'
@@ -21,10 +19,9 @@
   end
   spec.bindir        = 'exe'
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.add_development_dependency 'bundler', '~> 1.14'
-  spec.add_development_dependency 'rake', '~> 12.0'
-  spec.add_development_dependency 'rspec', '~> 3.6'
-  spec.add_development_dependency 'rubocop', '~> 0.48.1'
+  spec.add_development_dependency 'rake', '~> 12.3'
+  spec.add_development_dependency 'rspec', '~> 3.8'
+  spec.add_development_dependency 'rubocop', '~> 0.57.0' # highest supporting 2.1
 end