Converts an IEEE 754 number into a hex representation of it.
@param {number} value - Number to be converted into an hexadecimal string.
@param {object} options - Options configuration object.
@return {string} IEEE 754 hex representation of the number.
function num2hex(value, options) {
  if (value === undefined) throw new Error('Value is undefined');

  var buffer = Buffer.alloc(NUMBER_OF_BYTES);

  writeTobuffer(value, buffer);

  return buf2hex(buffer, options);
}