fixed article validations to allow blank volume and number
Merge pull request #13 from Mession/fix_article_validations

Fixed article validations to allow blank volume and number
created models, migrations and seeds for new super_reference
refactored old references_controller and its index view to test if listing super_references works

.travis.yml: make travis to run cucumber tests

Added some tests for articles_controller

Added a test for article's to_s method

Publisher and address fields back

Modified show and form
major changes to references, see comments
Yritetty saada joitakin testejä toimimaan