added authentication filters to levels_controller and users_controller
fixed bug where button to next level could be obscured by leftover blocks
added status bar to Levels#show
added method to return a User's best score for a particular level
added timer functionality to levels
fixed best_score bug when users had not completed a given level
moved status_bar and score_form from Levels#show into partials
created help partial and added it to Levels#show