allow list=-1 in Item model (will be used for challenges)
add challenge option in items form
dont display challenges in home; fix list_name
display challenge label on items
better items table design
create controller action and route for home#challenges
WIP home#challenges
extract scores into a partial
add link to challenges in home#index
display and design challenge list
bugfix controller challenges
display message when no challenge; remove scores in home#challenges
move challenges link in home#index
remove link on home page