localozation for feature and step files

Hi there,

based on the works of DrDub (pull request #6) and the sheriff's comments, I've worked on the localization of feature and step files.

The user may now write feature and step files in more than 60 languages (call "pherkin --i18n help" to see which ones). The new directory "i18n" contains a German translation of the calculator.

Please review and comment. I'd be happy to see my changes merged in.

Regards,
  Gregor