Feature request: extract the BSON library into its own module

[tomtaylor]

It'd be really useful to be able to use BSON as a generic, schema-less, binary serialization format. It looks like the code for encoding/decoding BSON is fairly separate, but it'd be great if it could be extracted into it's own module for those who aren't using mongodb.

I'd happily do this myself, but I'm not sure where to start - my C knowledge is pretty basic. If you have any pointers (BADOOMTSSHHH) that'd be great.