Putting data into list
Drawing the polygons now, clearly the true block geom needs to be drawn rather than the bounding box approximation.
Now plotting really pleasant looking map.
The arachnoid find area works, using the log scale on density but need to convert to better units that square degrees.
Messing around with colorization, really need to move into ipython
Clipping the alpha value, though other values need clipping too.  I'm thinking what I'd like to be able to do is have a colorized histogram of population density- a 2 value map where the boundary between the denser half of the population and the sparser half, and variations with quartiles, deciles, but retaining the ability to see where the halves are, and divisions between the halves, without being too confusing.