Added missing closing tags.

Modern browsers are pretty smart about guessing where to put in the
closing tags, but not closing tags is a good way to introduce bugs in
the markup.
Separated layout and content.

Some divs had bootstrap classes for layout, like "row", and were also
being used to hold content. This was causing problems with the margins,
and putting some of the SVG elements out of alignment.

In general, bootstrap layout divs should never be used to hold content
directly.
Broke description text into paragraphs.

Using <p> tags instead of line breaks to separate paragraphs. Also moved
the style rules for <p> into the <style> section, so we don't have to
write it inline for every paragraph.
Calculate size of SVG based on page size.

Based on this article:
http://blog.apps.npr.org/2014/05/19/responsive-charts.html