Cancancan

https://github.com/openSUSE/osem/issues/23

Some issues that I have not been able to solve yet are:

* Ability is not applied(?)
https://github.com/differentreality/osem/blob/cancancan/app/models/ability.rb#L103
Browser shows the new commercial page, test fails: 
https://github.com/differentreality/osem/blob/cancancan/spec/features/commercials_spec.rb#L22

Failures:
  1) Commercial organizer behaves like adds and updates a commercial of a conference
     Failure/Error: select('SlideShare', from: 'commercial_commercial_type')
     Capybara::ElementNotFound:
       Unable to find select box "commercial_commercial_type"
     Shared Example Group: "adds and updates a commercial" called from ./spec/features/commercials_spec.rb:65
     # ./spec/features/commercials_spec.rb:23:in `block (3 levels) in <top (required)>'
     # ./spec/spec_helper.rb:60:in `block (3 levels) in <top (required)>'
     # ./spec/spec_helper.rb:59:in `block (2 levels) in <top (required)>'

* I got failing tests which I cannot reproduce in browser with commented lines in:
https://github.com/differentreality/osem/blob/cancancan/spec/features/ability_spec.rb#L86

Yes, I thought it is not a bad idea to still have an indication that there is an item pending (or done) in the todo list, without linking to the corresonding page of course. 

You might not be able to change that part of the conference, because you only have the 'cfp' role, but you can still be informed of what is going on with the progress (what is done, what isn't).