1. templated save_as_png and save_as_jpeg 2. use std::iostream for I/O in save_to_file
1. templated save_as_png and save_as_jpeg
2. use std::iostream for I/O in save_to_file

TODO: allow writing an output image to memory buffer (i.e Python StringIO)



git-svn-id: 5adfda8227e14e59fd47d5bd9925a30df16fed74@552 d397654b-2ff0-0310-9e29-ba003691a0f9

makinacorpus/mapnik2,makinacorpus/mapnik2,craigds/mapnik2,craigds/mapnik2,makinacorpus/mapnik2,makinacorpus/mapnik2,craigds/mapnik2,craigds/mapnik2