emulating gnuplot's x2label/y2label

I want to plot two quantities on the same graph such that

    > the X-axis remains the same, while the left and right
    > Y-axis show the ranges for the first and second quanties
    > respective. I fished through the demos (shared_axes etc),
    > the cookbook as well as the user manual, but haven't been
    > able to figure out a working example yet.

examples/two_scales.py

Hope this helps,
JDH