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.
pandoc filter to convert blockquotes to divs

This filter converts all blockquote-with-attributes to
div-with-attributes.

A blockquote-with-attributes is defined as a blockquote that has a
header with attributes defined on it as it's first element, e.g.

    > # valid blockquote {.class}
    > text

This example would be converted into this markdown:

    <div class='class' id=id>
    # valid blockquote
    text
    </div>

And the equivalent html.

The class must be one of the allowed classes defined in the filter (i.e.
one of 'callout', 'objectives' or 'challenge').
add pandoc dependencies to README
Merge pull request #9 from aaren/gh-pages

[RDY] pandoc filter to convert blockquotes to divs