Document number.positive() and number.negative().
Document number.positive() and number.negative().

tpiecora/joi,davidbenko9/joi,lloydbenson/joi,jagoda/joi,naitsric/joi,danielb2/joi,geminiyellow/joi,pikselpalette/joi,bananaoomarang/joi,ck-lee/joi,thethanghn/react-native-joi,robertherber/joi-extended,rmoorman/joi,opyate/joi,jeffbski/joi,cesarmarinhorj/joi