Serve static assets by default and use secure rubygems

the secure rubygems source is the new "standard" for bunder, so it makes sense to use it by default.  Bundler complains about it otherwise.

Also, since this wasn't immediately apparent to me when I started, I added to serve static assets from the javascripts directory and added a stylesheets directory.  This should make the startup cost near 0 after invoking the generator.

It may be worth it to also add an images directory.