div & span support

[Richard Taytor]

"Markdown is a text-to-HTML conversion tool for web writers."*

I have no interest in mapping more HTML tags to Markdown; however, div and span are simply fundamental if one needs to address multiple blocks as a unit and string segments which should not be otherwise formatted. Attribute support is also essential to my purposes.

I have no interest in threatening the Markdown community or defending/proving my perspective; I merely wish to cooperate with those who also find reason to extend it (if that's not you, then don't worry), and I do remain interested to engage in creative/constructive/useful discussion, critical or otherwise.

* I also understand its "overriding design goal".

--D