Waterfall Chart

Thanks for flot.

Here's an implementation of a waterfall chart (see
http://en.wikipedia.org/wiki/Waterfall_chart)

I've added an example/waterfall/index.html for you to check out the finished result.

There are a lot of features that could be improved on this implementation - e.g. the legend and outline colours to match fill colour. But it's quite useful in it's current state.

Warning: the waterfall code replaces the default drawSeries. I couldn't find an elegant way to override the parts I needed so have had to duplicate a lot of code in jquery.flot.waterfall.js and hack jquery.flot.js (which I'm not proud of ...)