Bump rails-reveal-js to 2.6.1.2
Move reveal to lectures js file that only loads on showing lectures
Organize the stylesheets to import bootstrap_overrides right after bootstrap
Add more sample lectures
Add method to group lectures together by year then by semester
Add active_li_link helper
Add index view for lectures
Load reveal stylesheets and javascripts on show only
Retab the sample lecture
Add default scope for lectures to order by the lecture number