Render Rails form errors with Twitter Bootstrap styles

form_errors.rb

# config/initializers/form_errors.rb
#
# Wraps a <div> tag around the field with an error with the 
# correct classes for Twitter bootstrap to style the inputs
# with errors correctly (red border/red box-shadow)

ActionView::Base.field_error_proc = Proc.new do |html_tag, instance_tag|
  "<div class='control-group error'>#{html_tag}</div>".html_safe
end