update autotest integration doc

features/Autotest.md

@@ -1,10 +1,17 @@
-The rspec:install generator creates a .rspec file, which tells RSpec to tell
-Autotest that you're using RSpec and Rails. You'll also need to add the ZenTest
-gem to your Gemfile:
+The `rspec:install` generator creates a `.rspec` file, which tells RSpec to
+tell Autotest that you're using RSpec. You'll also need to add the ZenTest and
+autotest-rails gems to your Gemfile:
 
-    gem "ZenTest"
+    gem "ZenTest", "~> 4.4.2"
+    gem "autotest-rails", "~> 4.1.0"
+
+If all of the gems in your Gemfile are installed in system gems, you can just
+type
+
+    autotest
+
+If Bundler is managing any gems for you directly (i.e. you've got `:git` or
+`:path` attributes in the Gemfile), however, you may need to run
+
+    bundle exec autotest
 
-At this point, if all of the gems in your Gemfile are installed in system gems,
-you can just type autotest. If, however, Bundler is managing any gems for you
-directly (i.e. you've got :git or :path attributes in the Gemfile), you'll need
-to run bundle exec autotest.