Document customize default-path configuration

Author: vivekmiyani

features/README.md

@@ -34,11 +34,15 @@ without having to type RAILS_ENV=test.
 
 Now you can run:
 
-    script/rails generate rspec:install
+    bundle exec rails generate rspec:install
 
 This adds the spec directory and some skeleton files, including a .rspec
 file.
 
+You can also customize the default spec path with `--default-path` option:
+
+    bundle exec rails generate rspec:install --default-path behaviour
+
 ## Issues
 
 The documentation for rspec-rails is a work in progress. We'll be adding