Grains exercise may need more tests

[Trevoke]

There's not much reason to write logic for the total method since it's never going to change: it's always the sum of all 64 squares. Why not add an argument for how many squares to count up to, and some tests to reflect that?

[Insti]

Which language is this?

It is useful to test that total returns the correct value, and in Ruby we have tests for the total and for the number of grains on some of the squares.

Closing this now, but if you want to you are welcome to create a pull request for the exercises/grains/canonical-data.json file that contains the tests you think are relevant.