free scales example--doesn't work yet

I thought we might want an example with ```free_y_axis=true```, but it isn't for me working yet. See https://github.com/dcjones/Gadfly.jl/issues/213.

I was looking at this in reply to a mailing list question: https://groups.google.com/forum/#!topic/julia-users/5kIL-Xrh1Lk