Add puppet-lint-unquoted_string-check to Gemfile

Gemfile

 source ENV['GEM_SOURCE'] || "https://rubygems.org"
 
 group :development, :unit_tests do
-  gem 'rake',                    :require => false
-  gem 'rspec-puppet',            :require => false, :git => 'https://github.com/rodjek/rspec-puppet.git'
-  gem 'puppetlabs_spec_helper',  :require => false
-  gem 'puppet-lint', '< 1.1.0',  :require => false
-  gem 'simplecov',               :require => false
-  gem 'rspec-puppet-facts',      :require => false
-  gem 'json',                    :require => false
-  gem 'metadata-json-lint',      :require => false
+  gem 'rake',                               :require => false
+  gem 'rspec-puppet',                       :require => false, :git => 'https://github.com/rodjek/rspec-puppet.git'
+  gem 'puppetlabs_spec_helper',             :require => false
+  gem 'puppet-lint', '< 1.1.0',             :require => false
+  gem 'puppet-lint-unquoted_string-check',  :require => false
+  gem 'simplecov',                          :require => false
+  gem 'rspec-puppet-facts',                 :require => false
+  gem 'json',                               :require => false
+  gem 'metadata-json-lint',                 :require => false
 end
 
 group :system_tests do