Cleanup ruby code via rubocop

This commit will add code cleanup as corrected
and alerted by rubocop. It also adds rules to
execute rubocop on Travis.

spec/spec_helper_acceptance.rb

@@ -6,11 +6,11 @@ run_puppet_install_helper
 install_module_on(hosts)
 install_module_dependencies_on(hosts)
 
-UNSUPPORTED_PLATFORMS = [ "Darwin", "windows" ]
+UNSUPPORTED_PLATFORMS = %w[Darwin windows].freeze
 
-unless ENV["RS_PROVISION"] == "no" or ENV["BEAKER_provision"] == "no"
+unless ENV['RS_PROVISION'] == 'no' || ENV['BEAKER_provision'] == 'no'
   hosts.each do |host|
-    install_puppet_module_via_pmt_on(host, {module_name: 'puppetlabs-apt'})
+    install_puppet_module_via_pmt_on(host, module_name: 'puppetlabs-apt')
   end
 end