* Rivers and grayscale_heightmaps are generated as PNG images, filenames no longer have to be provided.
* The grayscale_heightmap is now stored as a proper 16 bit grayscale PNG.
* Modified color elevation routines so that depressions are still represented as land instead of ocean and heights are normalied.
* Speed of generation increased by almost a factor of 3 (due to update to Platec and making heavy use of numpy).
* World-generation is now deterministic, i.e. generation is 100% reproducible.
* Added support for exporting heightmaps using libgdal (see http://www.gdal.org/formats_list.html for possible formats).
* Added the ability to modify temperature and humidity ranges as well as the temperature/precipitation curve.
* Added the ability to generate scatter plots showing temperature and humidity of all terrestrial cells.
* Added small variations to the temperature-map based on basic orbital parameters.
* Added a satellite-like view of the world.
* Added support to save/load worlds in/from HDF5-format.
* Removed support for saving/loading worlds in/from pickle-format.