Improve guard-rspec config (fail-fast and restart all)

Guardfile

@@ -4,7 +4,7 @@ guard :cucumber, cli: '--format pretty --quiet' do
   watch(%r{\Afeatures/step_definitions/.+_steps\.rb\z}) { 'features' }
 end
 
-guard :rspec do
+guard :rspec, cmd: 'rspec -f doc', all_after_pass: true do
   watch(%r{\Aspec/.+_spec\.rb\z})
   watch(%r{\Alib/(.+)\.rb\z})     { |m| "spec/#{m[1]}_spec.rb" }
   watch('spec/spec_helper.rb')    { 'spec' }