backward compat fix for geos < 3
remove 2.2.3 geos version restriction (now accept geos >= 2.2.3)
fixes for geos 3
added proj4string attribute.
For non-Agg backends, handle inf as nan in path iterator
fix another typo
add colorbar, more labels.
update comments.
updated testgdal
update testgdal example (now exercises more gdal features)
