Spread operator in combination with a set is incorrectly transpiled

[flekschas]

The following statement...

console.log([...new Set([1,2,2])]);
// => [1, 2]

...is unfortunately transpiled by Buble the code into:

console.log([].concat( new Set([1,2,3]) ));
// => [Set(3)]

But the statements are functionally not equivalent. I would expect Buble to either handle the spread operator correctly or throw a warning or error.

This is potentially related to #81

[adrianheine]

This topic has been discussed somewhat in #81.

[adrianheine]

Closing this in favor of #131.