I am using Nitrous.io for a while and liked it very much! When I am developing with Ruby/Rails, I use better_errors gem.
If you are working local and using localhost, there is no problem - better_errors working well. But if you develop on a virtual machine or cloud, You should make a small change in
Add this line to the file
Tip: You can find YOURENVIP, by pressing Toggle env dump link.
Restart the server and voila !