README.md in ruby-clock-0.8.0.rc2 vs README.md in ruby-clock-0.8.0.rc3

@@ -136,22 +136,25 @@
 Read [the rufus-scheduler documentation](https://github.com/jmettraux/rufus-scheduler/#callbacks)
 to learn how to do this. Where the documentation references `s`, you should use `schedule`.
 
 ### Shell commands
 
-You can run shell commands in your jobs. They are invoked using
-[posix-spawn](https://github.com/rtomayko/posix-spawn), which means
-the ruby process is not forked.
+You can run shell commands in your jobs.
 
 ```ruby
 schedule.every '1 day' do
   shell('sh scripts/process_stuff.sh')
 end
 ```
 
-`shell` is a very simple convenience method which is implemented with
-[terrapin](https://github.com/thoughtbot/terrapin). If you want to use other terrapin
-features you can do so:
+By default they will be run with
+[ruby backticks](https://livebook.manning.com/concept/ruby/backtick).
+For better performance, install the [terrapin](https://github.com/thoughtbot/terrapin)
+and [posix-spawn](https://github.com/rtomayko/posix-spawn) gems.
+
+`shell` is a convenience method which just passes the string on.
+If you want to use other terrapin features, you can skip the `shell` command
+and use terrapin directly:
 
 ```ruby
 schedule.every '1 day' do
   line = Terrapin::CommandLine.new('optimize_png', ":file")
   Organization.with_new_logos.find_each do |o|