hsluv2rgb returns values outside the 0-1 range

[tko]

Modifying the test suite slightly to add assertions the returned rgb values are in [0,1] range as documented makes the tests fail for several cases, '#ffdd00' for example.

Admittedly the error is only in the 1e-14 range so absolutely tiny, but enough to trip assertions if those values are passed along to other function that validate their inputs.