this cucumber feature follows the likely steps a theme designer would take
to build a Rubygem of his theme starting from the scaffolding generated by
`jekyll new-theme` command and further checks if the gem built actually
has the files he planned to include.
* Move step_definitions/jekyll.rb to just step_definitions.rb
* Rename the formatter to Jekyll::Cucumber::Formatter, it's Jekyll's.
* Add some flair; switch to checks!
* Rename env.rb to helpers.rb