mod2#implement `search_by_title` on the video model
mod2#implement search on the UI
mod2#implement `recent_videos` method on the category model
mod2#show only recent videos on the UI
mod2#implement the front page, register page and sign in page
mod2#add authentication
mod3#add controller tests for videos#show and videos#search
mod3#add controller tests for authentication
mod3#add video reviews
mod3#user can review a video