FIX: Pass a C-contiguous array to points_in_polygon

[jwiggins]

Fixes #408

[corranwebster]

Looks good to me.

Are there other places where we call points_in_polygon that may have similar problems?

[jwiggins]

I had the same question. This is the only other call to points_in_polygon:

$ grin points_in_polygon
./chaco/polygon_plot.py:
   12 : from kiva.api import points_in_polygon
  138 :         if points_in_polygon([data_pt], poly)[0] == 1:

It's passing a list, which gets passed through numpy.asarray before constructing a view. I think it should be OK.