Add support for trailing comma in function arguments

[olessavluk]

Fixes #453

I've tested this using make test and also installed patched version locally. For now there are no errors/warnings for this code:

Trailing comma in: import, function declaration/call, array, object, export

import {
  a,
  b,
} from 'package';

function f (
  a,
  b,
) {}

f(
  1,
  2,
);

const array = [
  1,
  2,
];

const object = {
  a,
  b,
};

export {
  a,
  f,
};

[dgutov]

Thanks!