"Fancy annotation" parsing for ES6 methods

[jareware]

One might expect the "fancy annotations" (as in here) to work also on ES6 methods, such as:

var o = {
    /* : (x: string, y: number): boolean */
    foo(x, y) {
        return x.length * y === 5;
    }
};

but they currently don't, due to the comment block being assigned to the AST slightly differently.

See https://github.com/jareware/flotate/pull/4 for a related fix.