Prompt to install more up-to-date version

README.md

@@ -39,7 +39,7 @@ FriendlyId offers many advanced features, including:
 Add this line to your application's Gemfile:
 
 ```ruby
-gem 'friendly_id', '~> 5.4.0'
+gem 'friendly_id', '~> 5.5.0'
 ```
 
 Note: You MUST use 5.0.0 or greater for Rails 4.0+.