Add ' to "require resque/server" in README.markdown

Author: federomero

README.markdown

@@ -491,7 +491,7 @@ HTTP basic auth).
 
 ### Rails 3
 
-You can also mount Resque on a subpath in your existing Rails 3 app by adding `require resque/server` to the top of your routes file or in an initializer then adding this to `routes.rb`:
+You can also mount Resque on a subpath in your existing Rails 3 app by adding `require 'resque/server'` to the top of your routes file or in an initializer then adding this to `routes.rb`:
 
 ``` ruby
 mount Resque::Server.new, :at => "/resque"