Looking at https://en.wikipedia.org/wiki/Number it seems that Integer is "special" -- every other number type is listed as "<adjective> numbers" (e.g. rational numbers, complex numbers) but integers are listed as "Integers". So let's just switch it to that, and keep Integral as an alias for backwards compatibility. I don't think it's a huge problem to fix this in 3.7b2, if someone wants to do the work.