Add Made with love tagline to index view.

- Include stylesheet reference to Symbolset Standard webfont in layout.
- Add text and heart icon to footer element in index view.
Use Sprockets gem to compile and serve web assets.

- Include sprockets gem in bundler.
- Move css/images/webfonts from public/ to assets/.
- Setup sprockets in config.ru.
- Create application.css to define require order.
- Update old public/ references to new assets/ references.
- Include sprockets to list of Open Source Usage in readme.