support node v6

[eleith]

nextjs currently supports node v6, but using next-optimized-images fails when imported with the following

./node_modules/next-optimized-images/index.js:93
          ),
          ^

SyntaxError: Unexpected token )

i believe this is because node v6 doesn't support trailing commas. there might be other issues, this is just the first error i hit. i'm exploring now if v6 is fully unsupported or if there are existing workarounds.

[eleith]

not all dangling commas are a problem, but they seem to be in function calls. in particular, this will trip up node v6

const a = Object.assign(
    {"a": 1},
    {"b": 2},
  );

but this will work

const a = Object.assign(
    {"a": 1},
    {"b": 2}
  );

[cyrilwanner]

Thanks again for reporting this issue and directly creating a PR to fix it :)
Your fix is now published on npm with version 1.4.1