Odi tweaks

Hi Ben

I've made a few tweaks here:

* remove `.ruby-version` and set up ruby version and gemset in the Gemfile
* allow an optional logo on the Submit page (could probably use some design magic)
* redirect _/_ to something more useful for our users (configurable in _config/config.yml_)
Probably should add `config/config.yml` to `.gitignore` and add a `config/.gitkeep` file or a `.config/config_example.yml`