Continue troublshooting zero-length files & requests.
removed extraneous listen_address var.

misc. refactoring in attempt to figure out OS X semaphores.
fixed sem_unlink() bug and request buffer parse bug

sem_unlink() should come after sem_open() so the semaphore is
immediately close on program exit. The response buffer was null
terminated one character too soon, fixed by using the parser's nread
var instead of state's nread (now deleted).
Fixed empty request body error. Added MIME type detection.

Bugfixes & minor refactoring and string wording.