add: loop.h, epoll/hadler.h and kqueue/hadler.h has been added.
remove: epoll/loop.h and kqueue/loop.h has been removed.
add: inline function loop_exception has been added.
change: reader.c and writer.c has been merged to reader_writer.c.
fix: should remove unused files.
change: epoll/loop.c and kqueue/loop.c has been amalgamated to src/loop.c.
remove: epoll/loop.c and kqueue/loop.c has been removed.