Quit if not supported OS

Currently, we support linux only, definitely.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Receive screen and left/top/right/bottom argument

To make it more felxible, receive desired screen, left, top, righr,
bottom coordinate and permit -1 as argument's value which means current
window's coordinate for that argument.

Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Update README for usage, license and author info

Signed-off-by: SeongJae Park <sj38.park@gmail.com>