Added functionality to 'sniff' out a default way to display a source as a raw raster reader.
Added functionality to 'sniff' out a default way
to display a source as a raw raster reader.

if it only has one band use that.
if it has a red, blue, and green colorinterp
dislay those bands as an rgb image.
else display the first band.

brendan-ward/rasterio,brendan-ward/rasterio,brendan-ward/rasterio