README.md in exercism-0.0.8 vs README.md in exercism-0.0.9

@@ -22,9 +22,13 @@
 
     $ exercism submit example.rb
 
 This submits `example.rb` on your current assignment.
 
+    $ export EXERCISM_ENV=development
+
+Reveals stack traces on errors.
+
 ## Contributing
 
 1. Fork it
 2. Create your feature branch (`git checkout -b my-new-feature`)
 3. Commit your changes (`git commit -am 'Add some feature'`)