fix version in README

Author: Ruslan Korolev

README.md

@@ -4,7 +4,7 @@ Haml-rails provides Haml generators for Rails 4. It also enables Haml as the tem
 
 To use it, add this line to your Gemfile:
 
-    gem "haml-rails"
+    gem "haml-rails", "~> 0.8"
 
 This ensures that:
   * Any time you generate a controller or scaffold, you'll get Haml templates (instead of ERB)