Add another resource to README on DDD in Ruby.
Add another resource to README on DDD in Ruby.

jbpadgett/ddd_sample_app_ruby,jbpadgett/ddd_sample_app_ruby,jbpadgett/ddd_sample_app_ruby,makenoisewacamayo/ddd_sample_app_ruby,makenoisewacamayo/ddd_sample_app_ruby,makenoisewacamayo/ddd_sample_app_ruby,paulrayner/ddd_sample_app_ruby,paulrayner/ddd_sample_app_ruby