This is backwards-compatible, yet adds numerous features to d3.xhr. You can now:
* Use standard node-style callbacks (fixes#473).
* Abort in-flight requests.
* Listen for progress events.
* Listen for load, error and abort events separately.
* Make POST requests (or any other method), including data.
* Set arbitrary request headers.
* Have multiple listeners on requests.
Rather than producing separate files for each module, the default build now
produces a single file. This should encourage better page-load performance as
the files were relatively small. Also, it's easier to deal with only one file
rather than many, especially if you're not quite sure what the dependencies are.
You may still create minimized builds, if you don't want every feature.
This commit also demotes the chart components to the examples directory, rather
than keeping them as part of the core library. As always, D3 is not a charting
library, and these were ever only intended to serve as examples.
Mike Bostock