Added Bootstrap and query. Refactored leaderboard --> Engagement Index

Added the bootstrap gem, and manually added the jquery file in the vendor's folder. Also added a tiny bit of bootstrap onto the engagement index page to test out the bootstrap

@christianv, @richcreationsrc and I were looking at the Canvas designs and stylesheets and it looks like the model their design heavily on boostrap's UI. Since this project is a proof of concept, we'd want to balance speed alongside viewability, and since Canvas already styles very similarly to bootstrap, it's a double plus to include it here.