Re-imagined README.md for rails applications

You mean to generate this as default doc/README_FOR_APP?

My suggestion is to generate this as the main README file.

Thanks for committing a version of my suggestion.

https://github.com/rails/rails/commit/6cf47c533d7d6784d34fc31406a335555e0c32b8#railties/lib/rails/generators/rails/app/templates/README