Added rolify, cancan and better_errors to gemfile
Added binding_of_caller gem to support better_errors.
Generated ability class for cancan.
Ran rolify generator.
Updatedb schema.
Added wirble syntax highlighting to development env.
Updated ability class.
Updated schema
Updated ability class
Removed require nokogiri from lessons model.
Added rolify to Chapter and Lesson model.
Added laod_and_authorize_resource to controllers which should be controlled by cancan/rolify.
Routing the user back to application root if she is not allowed to access a resource.
Added exception message when access is denied to resource.
Allow any user to check if she supplied a correct answer to her question.
Added Link-helpers for devise.
Updated Chapter view, so that only users with respective abilities can edit and create lessons.
Updated application view so that approved users see Lessons in navigation.
Updated edit links in views. !
Removed superfluous application helper for cancan.