bs
==
pixel-wise background subtraction


update:

@date 2012-10-08: simplified the interfaces 
@note: I plan to refactor the codes in the future. maybe I could model the 
foreground pixels in the time-domain too, which will be much useful (we could 
modeling the background and in the same time modeling the foreground?). stay tuned.

@date 2012-03-15: added new C version in bs.h and bs.c, testing example in bs_example.cpp