Documentation request for subplots

[npmurphy]

Some clarification of how to make and use subplots in the documentation or an example in XPlot/src/XPlot.Plotly/Tests/Subplots.fsx would be very helpful.

I have gotten this far, two axes are made but they are overlaid, and only one plot is visible.

#I "packages/XPlot.Plotly/lib/net45"
#I "packages/Newtonsoft.Json/lib/net45"
#r "XPlot.Plotly.dll"

open XPlot.Plotly
let layout = 
    Layout(
        title = "Heatmap and Time Series Plot beside each other",
        xaxis = Xaxis(),
        yaxis = Yaxis(),
        xaxis2 = Xaxis(),
        yaxis2 = Yaxis()
    )

let data = [ Heatmap(z=[ [ 1;3;4]; [6;4;2]; [8;5;4]]):> XPlot.Plotly.Graph.Trace
             Scatter( y = [1; 3; 6],  xaxis="x2", yaxis="y2") :> XPlot.Plotly.Graph.Trace ]

data 
    |> Chart.Plot
    |> Chart.WithLayout layout