Add some number inequality check functions

[leonerd]

You can easily use is() to check if a number is exactly a given value, or use the Test2::Tools::Compare::float() function to make it approximate. But sometimes you want to test a number using one of the inequality operators. It'd be great if we had something like

$check = number_gt $min; # uses >
$check = number_ge $min; # uses >=
$check = number_le $max; # uses <=
$check = number_lt $max; # uses <

This would be especially useful combined with supporting is()-like testing in is_refcount() (#259).

[exodist]

comment moved to correct issue