Rename system to features

Author: michael-misshore

spec/system/fetch_critical_css_spec.rb renamed to spec/features/generate_and_fetch_critical_css_spec.rb

@@ -1,6 +1,6 @@
 require 'spec_helper.rb'
 
-RSpec.describe 'fetching the critical css' do
+RSpec.describe 'generate and fetch the critical css' do
   before do
     CriticalPathCss.generate_all
   end