How to attach properties other than x,y,y0 to a layer of streamgraph in d3?

I am a d3 newbie and I've been trying to customize the Streamgraph example (http://mbostock.github.com/d3/ex/stream.html):

I have run into some issues:

I want to assign a custom data property (for examples sake, lets just say its a label called "type") to each layer in the stream so that when you hover over that layer, a popup box appears with the "type" listed for that layer.

When I input my data source into the graph I use this code:

      vis.selectAll("path")
        .data(data0)
      .enter().append("path")

The graph only seems to take data of the format:

            [
                 [
                    {
                        "x": 0,
                        "y": 91,
                        "y0": 1.11
                    },
                    {
                        "x": 1,
                        "y": 290,
                        "y0": 1.11
                    }
                ],  
                [
                    {
                        "x": 0,
                        "y": 9,
                        "y0": 1.11
                    },
                    {
                        "x": 1,
                        "y": 49,
                        "y0": 1.11
                    }
                 ]
             ]

Where each sub-array above corresponds to a layer in the streamgraph.

How can I pass data to the graph that allows me to add an extra "type" property for each layer?

Basically so that when I refer to the datum of a layer, I can just type something like d.type and extract that property?

I originally came up with a really hackish way to do it:

                [
                    {
                        "x": 0,
                        "y": 9,
                        "y0": 1.11,
                        "type": "listings"
                    },
                    {
                        "x": 1,
                        "y": 49,
                        "y0": 1.11,
                    }
                 ]

and then I refer to it in the layer datum by saying d[0].type, but this doesn't seem like the proper way to do it.

Use stack.values, and then wrap each layer's data points with some additional data for the layer. Your data will look something like this:

[
  {
    "type": "apples",
    "values": [
      { "x": 0, "y":  91},
      { "x": 1, "y": 290}
    ]
  },
  {  
    "type": "oranges",
    "values": [
      { "x": 0, "y":  9},
      { "x": 1, "y": 49}
    ]
  }
]

And the stack layout like this:

var stack = d3.layout.stack()
    .offset("wiggle")
    .values(function(d) { return d.values; });