added test for updating staff to deputy on employers page
implemented logic for update of staff member to deputy
added promote button to employer detail page to promote a staff member to deputy
#162 started to improve promotion dialog UI
#162 made promote dialog for students index prettier
#169 adapted rest promote/demote dialogs
#162 translated all promotion/demotion stuff to german
fixed demote bug
Merge branch 'develop-ja-promote-staff-to-deputy' of https://github.com/tkowark/hpi-hiwi-portal into develop-ja-promote-staff-to-deputy
#162 little fixes
#162 fixed some bugs
Merge pull request #307 from tkowark/develop-ja

#240 added security checks, and improved test coverage
fixed translaton
Merge remote branch 'origin/develop-ja' into develop-ja-promote-staff-to-deputy

Conflicts:
	app/assets/javascripts/students.js
	app/controllers/students_controller.rb
	app/controllers/users_controller.rb
	app/models/ability.rb
	app/views/employers/show.html.erb
	app/views/shared/_change_role_dialog.html.erb
	app/views/students/index.html.erb
	config/locales/views/students/de.yml
	config/locales/views/students/en.yml
	spec/controllers/employers_controller_spec.rb
	spec/controllers/students_controller_spec.rb
fixed merging issues
#162 changed userlist method to only return staff members of the users employer except the deputy
Merge remote-tracking branch 'origin/develop' into develop-ja-promote-staff-to-deputy
#162 fixed styling