add very basic gui
Merge branch 'gui'

* gui:
  add very basic gui
small fix: better naming
add create-world
use cell-coor instead of col + row in arguments of coor->color
use cell-coor instead of col+row in arguments of set-color!
implement swap-cells!
provide set-color!
add set-color! test
unify coordinates order to col+row
unify naming using American English
add colors->minority-index
implement minor?
add find-nearby-cells-helper
implement find-nearby-cells
implement find-free-spaces
implement get-neighbors-colors
fix find-nearby-cells
update in gui as coor->color has changed its arguments
add all-cells