Allow all formats supported by PIL

[wearpants]

It'd be handy to be able to generate an image in any of the formats supported by PIL. It looks as if that'd be as simple as renaming _generate_png to _generate_bytes or such, and passing the output_format argument through to PIL here: https://github.com/azaghal/pydenticon/blob/master/pydenticon/__init__.py#L247

[azaghal]

That would probably be quite a simple addition. As a curiosity, did you have a need on using generated identicons with some specific format?

Sorry for being unresponsive, been a bit busy, and this issue apparently slipped by me :)

[wearpants]

I was using this in Django with factory to generate data for user profiles in tests... don't recall the exact reason why I wanted something else out of PIL. Thanks for fixing!

[azaghal]

Implemented and pushed to master branch. However, transparency is currently handled properly only for the PNG format.