Default to use billing address for 1-1-stable

Hello, I'm using 1-1-stable branch of your gem. I made some changes in "_address.html.erb":
- By default, using "billing address for shipping" is checked.
- The shipping address class name must be "omega", not "alfa".
- Other little changes in the hr tag and commit button.
I only fixed this bugs in 1-1-stable, but I think this changes will work in other branches too. I hope you will find it useful.