added a new model stat_entry
Add new model StatEntry
Added views and controller for the StatEntry model
added devise modul for user login
added role management. there are 3 roles [admin, user (logged in), guest (not logged in]
admin can manage all
user can do everything except deleting cards
guest can only access cards#index and cards#show

roles are defined in models/ability.rb
to use permissions check you have to add authorize! [action] [element] to the specific function
e.g. def destroy
	@card = Card.find(params[:id])
	authorize! :destroy, @card
	...
     end
added some information to README in order to make role-feature working
Merge branch 'master' into create_stats
added permission check to StatEntry model
created relation between user and stat_entry model (stat entry belongs to a user, user has many stat entries)
fixed permission issues for deleting stat entries
added possibility to filter the stat entries
added username attribute for users
merged master branch into create_stats
added avatar and modified devise views
Merge branch 'master' into create_stats
merged with master branch and updated some views
added tabs to user dashboard
added highcharts module and integrated a pie chart to the view
added realname to users (not mandatory)
Merged Deck creation into master