app generator not including script.aculo.us with prototype

With the commit accepted in #5613 adding "-j" parameter for "rails new" command to add the --javascript and --skip_javascript options to the app generator, the wrong option is checked for when determining whether or not to include the script.aculo.us files when using Prototype (meaning this affects an app generated with default/no additional options).

The default javascript_expansions config expects these to be present, so they get included in the application layout and the log is littered with errors of no route matching the missing .js files.

The attached patch is a one-liner, plus tests. I've also submitted a pull request.