pair programming changes
moved product price validation to listing
remove redundant code
changed method name
refactor regular category routes
use reset_auth_token on session#destroy
refactored change_state method to use exception
removed redundant code
Merge branch 'master' of github.com:openlets/openlets-spa

Conflicts:
	app/controllers/api/v1/sessions_controller.rb
	client/app/core/services/user.coffee