failing test for grid
better failing test
make the test pass
failing test
use 'constructor style function' to avoid coupling
introduce point
make tests pass
remove dependency on map
simplify a little bit
remove a little bit of duplication
no commit to bound
probably the most complicated way imaginable
rename tick to tickCell
turns out an array will probably make tick harder, so refactor
write top level type signature
step back up, write failing test for live neighbours
leave a failing test
rename
we have Maybe, therefore we dont need cell state whatsoever
refactor from set to map