Fixed gitlab wiki page creation

Gitlab needs two non-standard HTML body attributes to work properly: data-page and data-project-id.
Since the whole JS is loaded at once, Gitlab uses 'data-page' for determining what the current page is in order do load proper JS for that page. 

The main JS dispatcher for Gitlab can be checked out here:
https://github.com/colab-community/gitlabhq/blob/master/app/assets/javascripts/dispatcher.js.coffee

The wiki button didn't work because the expression '$('body').attr('data-page')' returned 'undefined',  not loading any of the cases from that switch-case.