README.md in train-tax-calculator-2.3.2 vs README.md in train-tax-calculator-3.0.0

@@ -3,10 +3,10 @@
 ## Installation
 
 Add this line to your application's Gemfile:
 
 ```ruby
-gem 'train-tax-calculator'
+gem 'train-tax-calculator', '~> 3.0'
 ```
 
 And then execute:
 
     $ bundle