Rails framework and twitter bootstrap are good for your startup project, build-in generators generate source code by its way. It is a good starting point.

But I often have to change default generted source code:

• Add encoding: utf-8 into ruby file header, for Ruby 1.9.2 encoding.
• Change scaffold view files to apply bootstrap css.
• Other things you want to override default templates.

Rails provides the mechanism to custom generator behavior.

I have already got it, and source code is on github, follow README for usage.