Adding missing CSS files.

1. Bringing in Bootstrap CSS files.
2. Merging swc.css and swc-bootstrap.css from 'bc' repository.
3. Updating _includes/header.html to refer to the right files.
Preparing to create motivational slides
Converting `motivation.md` to use slides template.

Also modifed the Makefile to use the slides template for this file
instead of the generic template.

Note that we do not need a Markdown extension for deck.js because
Pandoc is doing Markdown-to-HTML conversion for us.
Merge pull request #13 from gvwilson/adding-slides

Adding slides
Fix layout to follow bc CSS
Merge pull request #14 from r-gaia-cs/fix-layout

Fix layout to follow bc CSS
Merge pull request #12 from gvwilson/adding-css-files

Adding missing CSS files.
Merge pull request #9 from aaren/gh-pages

[RDY] pandoc filter to convert blockquotes to divs