BD3WS.c: Added ability to immediately reuse socket with setsockopt(), fixing pesky failure-to-bind errors. Added Content-Type handler for application/octet-stream (though I'm likely to change the whole content negotiation process soon, so this was probably unnecessary).

BD3WS.h: Segregated header files by platform, the first step in (hopefully) eventual cross-platform compatibility (at least for Linux and Windows). Added the "application/octet-stream" string. Modified the default IP from localhost to 0.0.0.0, allowing for serving from all local machine IPs. Rearranged fields of the BD3WS_Client struct. Changed the log file handle into an actual FILE*, instead of an int.

README.md: Merged contents of todo.txt into the readme. This makes the todo list more visible through mediums like GitHub, and gets rid of an unnecessary text file. Also modified actual content of todo list.