implements some stubs and fixes some bugs
Merge branch 'develop' of https://github.com/dirkschumacher/iUPB into develop

# By Dirk Schumacher
# Via Dirk Schumacher
* 'develop' of https://github.com/dirkschumacher/iUPB:
  makes the breadcrumb look nicer :)
  adds an update method for posts
  adds an updated_at field
  hides price if no price is specified

Conflicts:
	app/controllers/ads_controller.rb
	app/views/ads/_form.html.erb
	app/views/ads/show.html.erb