Tweak % examples

[sogaiu]

This PR suggests tweaking some of the examples for %.

Looking at the first four, I got the sense that expressing all combinations of signs for the arguments was the intent:

(% 10 3) # -> 1
(% -10 3) # -> -1
(% 10 -3) # -> 1
(% -10 -3) # -> -1

The second set of four examples has been tweaked to match the pattern (as otherwise there are duplicate examples).

A similar change in sign was applied to (% -1.4 0) to make it (% 1.4 0) so that there were two distinct examples.

The last two examples also use nan? to make the result possibly less confusing.

[pepe]

LGTM