enable deployment to relative path
- delete cruft from config.ru
- make another absolute href relative
- if env variable RAILS_RELATIVE_URL_ROOT not set, make default app location '/'
- on local machine, assets map correctly to the subdirectory when RAILS_RELATIVE_URL_ROOT specified, e.g.:

$ RAILS_RELATIVE_URL_ROOT='/foo' rails server -p 3000

But not certain it will work in production.  Lots of problems listed here: https://github.com/rails/rails/issues/4308

- still need a test
specify default deployment directory of '/' with ENV.fetch not ||
Merge pull request #232 from jwhitt/enable-deployment-to-relative-path

enable deployment to relative path