A sparkline is just a tiny chart that fits in to
the flow of text. We can achieve this by using a span instead
of a div, and making the dimensions really small. They will
work well for any chart with a large x:y aspect ratio, like a line chart
or a bar chart but other kinds of charts
probably won't work so well. We'll also use a little bit of custom CSS to
hide the axes (see
the source
for details).