Example:
>>> from mapnik import *
>>> im = Image(200,200)
>> save_to_file('test.png',im) # Guess image type from file extension
>> save_to_file('test.png,'jpeg',im) # Explicitly save as JPEG
bool hit_test(double x, double y, double tol);
2. added image_view(unsigned x, unsigned y, unsigned width, unsigned height)
allowing to select region from image data e.g (in Python):
im = Image(2048,2048)
view = im.view(0,0,256,256)
save_to_file(filename,type, view)
3. changed envelope method to return vy value in datasource classes
4. features_at_point impl for shape and postgis plug-ins
