JsonNumber::isIntegral did not have the same semantic meaning as in json-schema

[sebastian-toepfer]

unsure if it is a bug in json-p spec or here.

in json-schema 0.0 or 1.0 are valid integer values, but not for JsonNumber::isIntegral.

instead of

public boolean isIntegral() {
  bigdecimal().scale() == 0
}

it should be

public boolean isIntegral() {
  bigdecimal().stripTrailingZeros().scale() <= 0
}