carbon.md

Vim

autocmd BufWritePre * :%s/\s\+$//e

Emacs

(add-hook 'before-save-hook 'delete-trailing-whitespace)

Textmate

http://blogobaggins.com/2009/03/31/waging-war-on-whitespace.html

In your existing codebase

find . -name '*.rb' | xargs perl -pi -e 's/ +$//'