testcase updates for max min edge cases

This clarifies the behavour of R.max and R.min where garbage input has been provided.

See #548
I don't think we want to document all of these degenerate cases. The docs say it takes an Array of Numbers and returns a Number. That's what we want to support, and that's what we should test. We shouldn't chain ourselves to a test suite that casts the implementation details in stone.