function close (actual, expected, maxDifference, message) {
  const actualDiff = (actual === expected) ? 0 : Math.abs(actual - expected)
  const result = actualDiff <= maxDifference
  message = message || (actual + ' should be within ' + maxDifference + ' (inclusive) of ' + expected + (result ? '' : '. Actual: ' + actualDiff))
  return { result, message, actual, expected }
}
Checks that the first two arguments are equal, or are numbers close enough to be considered equal
based on a specified maximum allowable difference.

@example assert.close(3.141, Math.PI, 0.001);

@param {Float} actual
@param {Float} expected
@param {Float} maxDifference (the maximum inclusive difference allowed between the actual and expected numbers)
@param {string} [message] Defaults to structured message
@returns {InfoObject}